i'll start off with the usual qualifiers:
a. i could be wrong about the whole thing.
b. if you don't agree, that's fine. these are just ideas.

that said, perhaps it would be good for folks to hear some ideas on how to help things run more smoothly when hired to be an opening act.

it seems as though the same mistakes keep getting made and perhaps this treatise will be of some benefit in correcting this. these are suggestions.

first off, i distrust the whole hierarchy thing. i have been the opening act thousands of times in every imaginable situation and have also played with quite a few headliners in the last few decades and my feeling is that it's really all the same. so when i say "opener," i'm speaking to someone on my own level. there is no judgement there. or evaluation. maybe it should be the "act that goes on first" or something. at some point or another, everyone more or less opens for everyone else, no need to make a big deal out of the hierarchy. the bigger band has bigger problems, there is no call to feel like they really have it made and your deal is no good. you may not want to do what they are doing. you may not be willing to do what they had to do to get the audience they have. this is all fine. in any case you have your situation and they have theirs. wishing you could change places with someone will lead to unhappiness.

here are some ideas on how to help things run smoother.

if you are the opener or in the opening band, don't put your stuff on the stage when you get there unless directed to do so. walking into the venue, even if you play there every week and you are roommates with the sound guy, and putting your bass drum case in the middle of the stage is a bad idea. there are all sorts of reasons.
it's not your space until the headliner is finished with their check.
the trade off is that they have to show up way earlier than you and stay way later and usually if the show succeeds or fails they have to take responsibility, so really the heat is on them, so give them some room.
the best idea is to show up on time and have a designate go in and talk to the stage manager and ask him or her what to do.
that way when you bring your gear in, you won't then have to move it again once you are loaded in.
the idea is to not inflict your trip on other people.
just wait and see what you told to do.
hang out and watch the other band check or whatever, but don't make a scene with your cell phone or horsing around or taking your instrument out and demonstrating how great you are, just let things develop and then make your move.

it's really bad form to go back and start putting stuff in a dressing room. even if you always had that room when you opened for so and so and "you know how great they are." sometimes the headliner has a big production and will need both rooms. it can be very awkward to go and tell the first band, "hey we need the room you have to leave." it's possible to avoid lots of chaos if you don't do anything as an opener unless you are invited to do so by someone of authority.
it's really not a good idea to put a bunch of things in the bigger dressing room, this happens over and over.
my suggestion would be to not put anything in either dressing room until you figure out the deal.
all the first act has to do is come down and do a soundcheck, if there's time, and usually you play very soon after that and then you can take off, so you technically don't need a dressing room. many times you just come straight from your house. if you get a dressing room that's cool, if it's a workable space, double cool. if not, don't sweat it, you can split pretty quick and your total time invested if you do it right is about three hours or less, from load in, soundcheck, play your set, and takeoff.

it's probably not a good idea to have more gear then the headliner band. and a longer soundcheck. and more demanding people. the second band hopes that you don't need to take up their channels on the console so they can just go out there and play. and it's really cool if they can leave their gear set up and not have to strike anything. it's really nice if the first band can just fit into the deal on every level and not cause problems.

no one in the second band wants your cd. unless they specifically ask. there is no need to pass them out. they should be able to go to your website and listen anyway. think of all the resources this saves.

try to be accommodating vis-a-vis the merch table. there can be fights over the space. if you always defer to the other act, things will go much better. if there are hassles with the space or argument over the seller being hired by the other band and being distracted by your fourteen titles and three shirt models, just pass on the whole thing. it's cool and actually probably better for you to just go stand by the merch table after your set and sell your stuff yourself. this can save you 20% also. once the headliner starts the probability of selling anything else drops substantially. go get paid and split or check out the other band. you are done. some headliners are really cool and say, "hey put your stuff out there we'll sell it for you and pay the percentage or charges out of our end." no need to be dismayed if this is not the case. if you keep the goal in mind of "getting your music to folks" instead of "oh my god i HAVE to make more money!!!!!" you will be happier and the end result will be better.

it's not a great idea to impose yourself on the other band socially. even if you are doing a run of dates with them, give them space. tread lightly in this regard. if someone wants to chat, they'll come find you. best to keep a low profile. do not go and hang out in their dressing room. do not go on the bus even if they invited you last night and you hung out and were oh so charming. leave them alone unless they ask. every time. just because you went to dinner with the bassist last night don't assume anything. leave everyone lots and lots of space. stay off the bus and out of the dressing room. if you do this, you will be remembered fondly.

never let a chance go by to not say anything.

there's a whole school of thought out there that if you draw attention to yourself and promote yourself and press the flesh, be aggressive and all that, that you will go far. this whole methodology creeps me out and it's really hard to be in the room with someone like this for more than a few seconds. (while out on a long tour run, this creep factor gets exponentially higher.) i seriously doubt the long term efficacy of the strategy. my guess is that it does more harm than good. being a jackass is just being a jackass, i fail to see how this advances one's cause. more of the common good would be served by writing some good music and playing really good and being a nice person. being kind won't really advance your career or lessen irritations or frustrations, but at least you aren't being a jackass. as i've grown older, my observation is that sometimes folks compensate for lack of effort on their music by being really self-centered or opinionated or rigid in their outlook.
my theory is to let the music do your talking for you rather than your own mouth. this won't really bring you fame or wealth or anything necessarily but we serve sentient beings better by making good music, not by talking about how great we are or tearing someone else down or inserting ourselves into the right situations and all that. things have to be win/win really. win/loose is ultimately loose/loose.

at the venue, i would not recommend working the room, so to speak and hammering folks for gigs. you are there to play the job you are playing. it's not the right time to be hitting the promoter up for his festival or whatever. or hitting the headliner up to play some other date. or asking if their agency would take you on. concentrate on the task at hand. try to play really good. and not bother others. also observe if your own sidemen violate this sensibility. if you hired a guitar player to back you up, and at the jobsite you find she's passing her own demo cd out and hitting everyone up for a gig, fire her. my experience is that you are going to be sorry working with a person that will do that. he/she is probably not the best sideperson you can get because otherwise they would be making sure the show goes well instead of focusing on some other event that probably won't even happen, at some other time than the time you are actually in. my guess is that a knuckleheadly type person is just that way, and there is no way to correct this other than to replace them.

do your part to make your own soundcheck go smoothly. if this is an elusive concept for you, work on that. typically you won't have much time, maybe zero time. you'll have to think on your feet. don't sweat if you are fine tuning things after doors open. don't be upset if the headliner goes over their SC time. don't even be upset if they are poking around and go over and totally make it where you don't get a SC at all. this is your time to learn that when you are the headliner, allow space for the opening band to soundcheck before doors open. it's not always possible to do this.

be very careful about your guest list. if you put a jackass on the list with all access passage, you will bear the responsibility. also keep the guest list very short. just because you have a gig and are opening for so and so, there is no need to go calling friends and trying to get folks into the show that may not be that interested in the first place. want to be highly thought of? try not having a guest list at all.

it's not the mark of a quality person to dive into the backstage beer and food. wait and see what the situation is. i'm not sure if that was ever cool to do. my outlook is that it's the mark of the Ultimate Cheeseball, to be fixated on what one can get for free. it doesn't make sense to go cobbing around on the deli tray when in all likelihood there are great restaurants in the neighborhood. go there instead, they'll be glad to see you.

do not bring your kids down to the gig to hang out backstage. even if they are, in your eyes, well behaved. i have never understood why a family would be sitting at home, with their own refrigerator and stove and cupboard, and mom has a gig opening up for a touring band, and the idea passes the committee that they should all load up and go eat the backstage food at the venue. hard to believe but it happens over and over. please stop doing this. no need to cheese out just because of a free sandwich. backstage food typically isn't very good anyway.

probably you are not going to be that well received by the audience. don't worry about it. if you really work on your music, and have something to say and play as well as you can, somebody is going to like it. the way folks spend their dough these days is to save money and go to fewer concerts. so they are trying to squeeze as much as they can out of it, which strangely does not compute to them getting there early to see some new music they might not have heard of. en masse they want to see the second act. don't worry if they talk during your set. just play like you are in your living room and have fun. in some ways, you have the best deal in the house. you get paid to be there, you have zero pressure in regard to the financial performance of the show, you get full run of the place. bask in this. my formula is if you play for 3000 people and 100 people like what you do that never heard you before, you are way ahead. even twenty or ten or one.

in terms of set times, shorter is better. if you are scheduled to play for thirty minutes and they trim off ten to hold the house, this is a blessing and not a problem. if you are asked, "how long do you want to play?" answer, "how long do you need me to play?" they will say, "well thirty or forty minutes." say, "how about twenty five?" they'll say "great!" the shorter the better the tighter the sweater in this regard.

to recap:
show up on time, play the alloted time and leave folks lots of space to do their thing. be nice, adjustable and positive. allow space in your conversational dealings. eat your own food. detach from the result. let your music do your talking.

here's a good strategy. make friends with the house sound person. be very nice to him/her. he or she will be running sound for you as the headliner probably has their own person with them. this is an asset. the house sound person knows the rig best, and while the sound won't be as loud, they know the room intimately and the gear also, so they can give you a very good deal sound wise. if the sound person likes you, you win. they can be your best advocate in future deals. treat this person well and things will go well for you. so many times in my life i've walked offstage thinking "man that was a rough show, i don't think anyone was listening." and the befriended sound person said, "man that was really cool! you are very easy to work with and it's been great having you here/hear. hey next time you are in town, you should come and headline at my friend's club, here's his number, if you have a cd i'll give it to him, your music would be perfect there." or some version of that. the house sound person can be your best asset.