Amazing amazing thread. Some seriously useful info in here.
So without reiterating too much, here's my thoughts.
1) Practice your set up and teardown and load out. Sounds silly but you need to know how fast you can do this and who is responsible for what. True every venue is different but once you know who's responsible for doing what, it makes set up really easy. Ok
easier. We would all start with the drum kit cause our drummer had a huge kit. We'd bring it in and set it roughly in place while he tweeked it. After the kit was done he would help with the other stuff. Everyone in the band learned how to set up everyone elses rigs from scratch. Which pedals go where, everything.
2) This brings me to another point. Get organized! Have cases for everything. Organize your "extra cable bag". Those little velcro straps are really handy, and combined with color coding things, you can get the cables you need without having to fight with untangling the spaghetti monster.
3) Have an emergency kit of some kind. I had a leather duffle bag that had extra strings, straps, picks of various thicknesses, all kinds of batteries, a beat up boss distortion pedal and delay pedal, a roll of "gaffers tape", band-aids (pun?), extension cords, powerstrips, all of the guitar tools I could think of, you name it it was in there. We rarely needed it, but when we did we all said a prayer of thanks to whatever gods watch over gigging musicians.
4) Be cool with the other bands in your area because you'll never know when one of these bands could hook you up with a gig. Get to know who's out there. I have restrung guitars for bands that are on stage cause they had no one else to do it. I've even let a guy use one of my guitars while I did a quick fix on his during a song. I don't recommend the loaner thing but the plus side is they remembered us and got us a gig with them that we wouldn't have had other wise.
5) Scale your gear to the venue. If you're playing a small coffee shop gig DO NOT bring the 9 piece metal kit and the "Wall of Noise". I always tried to go to the location prior to the gig so that I could get a sense of how much space was available, what things they were supplying, what they weren't supplying, etc... This is a great time to talk with the manager if the place doesn't usually have live music and figure out placement of equipment verses traffic flow etc. If you have the luxury of a little time, going to the venue and getting this information a week or two in advance lets your scale back your gear if needed and go through your set with the new configuration of equipment. Which brings me to my next point:
6) FIGURE OUT WHERE THE PLACE IS BEFORE THE NIGHT OF THE GIG! Seems obvious, and I know its not always do-able but...
7) When designing your bands logo make sure its legible from more than 10 feet away. I love some crazy deathmetal shows but come on guys make a logo we can read. Maybe, just maybe somebody will like what they hear but they can't read the logo so you dont get the booking.
8) This seems obvious but I gotta say it: If you have any kind of merchandise bring it! It does no good sitting in grandmas basement. If you don't have a CD or T-shirts are out of the budget, grab your digital camera, snap some pics of the band, and get them printed. How many people have a photo printer at home these days? Even if the budget is tight spend the little extra cash, get the good glossy paper and print off 100 of them. It'll still be cheaper than shirts. Just make sure you have the band logo and some contact info in there somewhere. Have something for people to take home with them and remember you by.
9) Any documents or business cards need to be flat and clean. A business card pulled out of your pocket thats all crumpled up and covered in taco grease is not going to get you any work. At least none that pays. If you carry cards on you, as opposed to in your bass case, get one of those metal card holder things. Clean documentation (business contracts with the facility for example) is key to presenting yourself as a professional and reliable act.
Obviously we do this because we all love it, however you have to treat it like a business and present yourself and your act as a legitamate entity if you want to make any money at this. If you treat your commodity (the band) like a professional business, it is more likely that the club owner will as well.