lol why is everyone so down about their first jam experiences hahaha.. For me the most important thing is the musical preference. The band members must like all the stuff you plan to play. If you have one or two members who dun like jamming to Nickelback, better not even GO there. This is what I did before I started jamming with the band members; got it off a website.
1) everybody list down the bands that they like (past and present; contemporary etc)
2) circle the ones you guys have in common.
3) choose a couple of bands to start with: choose a few songs from each band.. one guy go home, dl all the tabs, email to everyone + the mp3s
4) one week later jamming lorr... sure no problem.
5) never get a satriani influenced guitarist.

you'll never get him to stop. ergo, prepare shovel instead. use appropriately.

6) screamers = can't sing. see number 5 for solution.