I'm in a reasonably "successful" band in my area, meaning we play the larger rooms, and the formula that seems to keep us there is to pick songs that are:
1) Instantly recognizable (nothing lets the air out of a room like a cover band playing a song nobody knows... leave that for original bands)
2) Uptempo and danceable (not everyone dances, but when people are dancing, it sets the party atmosphere)
3) Appeal to women (men don't care what the band plays as long as women are there)
4) Sound good when we cover them (e.g., don't pick songs you don't cover well, either instrumentally or (most importantly) vocally)
5) You can at least fake like you're enjoying playing (energy transfers to the audience)
This is really, really good. The next band I form or join will have to take this on board. I spent time last year trying to convince the 2 bands I was in that these were the principles to follow. One was folded by the band leader because he wasn't interested in any compromise; the other band I quit, and although they were working towards this goal it was too little to late. Both bands convinced an agent to give then a tryout gig, and then squandered the opportunity with an inappropriate song selection.
I'd like to add is my version of the above.
In order of importance:
Song choice...... you don't feed alligators hay......give them what they want
Energy/Excitement......This will take even a bunch of beginners a long way....pros would do well to remember that.
Visuals.....In this day and age slacks and polo shirts probably don’t cut it. Except for Balls and Weddings, DRESS UP. Next band I'm in I'm going to create a character for myself. It will make it more fun for me, and give people something to comment on.
Flow.....As someone else has already said, move to the next song with no breaks, chatter, or jokes.
Tightness....This is a long way down the list. Most bands spend months practicing stuff to get it "tight". FOR WHAT? The audience truly don’t care if all of the above are in place. They won’t notice if the verse/chorus arrangement is mixed up, the words are wrong. Just get tops and tails right and get out there and work.
I asked a similar question on TGP a couple of weeks ago and some of the song suggestions lead to a small epiphany. It caused me to go looking for well known dance tunes with simple arrangements and chord progressions.
In 15 minutes I found 10 tunes that only had 4 chords for the whole song. This includes tunes by Das Punk, the Neville Bros, Jamiriqoi, Kool and the gang etc.
This kind of simple music will be the focus of my next commercial band. I’m totally over tunes that have complicated arrangements. There’s always one or two people who can’t remember arrangements and these practices bore me to tears. That time should be spent on groove and feel and energy.