Be tight, know the songs like the back of your hand, show enthusiasm for the material (IE rock out but don't overdo it), dress like you belong in the band and would fit into a photoshoot or show easily, and hope they get along with you on a personal level.
Avoid: Kissing ass. This can be the wost thing ever when auditioning new members, as it's weird playing with someone who's "starstruck." Also avoid criticizing too much in an effort to not kiss ass, nobody wants to be a jackass.
As long as you're 1. On time (rationally speaking, there's no such thing as early, just on time or late), 2. know the material and play it tightly, 3. look/act like you're enjoying yourself and are fun to be around 4. have your equipment in good shape and setup time down to a minimum, you're golden.