If you have never used a professional band photographer, here are some factors you should be aware of and consider:
The Photographer: Make sure your photographer knows how to shoot bands. Beware of photographers with lots of expensive equipment, but no real experience in photographing live music. Check out their advertising and website and see if they say anything about music; or are they really a wedding, little league, or high school graduation photographer. Ask them what venues and clubs they've worked in, and what bands they have photographed. Most importantly, ask what they've done with bands you know, and ask your fellow musicians.
The Venue: If you want live performance shots, you (or your photographer) will need to know the size and elevation of the stage, the dimensions and visual barriers of the room, and the house lighting system. If you have the choice of a few different gigs you are playing in the near future, pick the venue with the best stage lighting and fog effets for your photoshoot. The more colorful and exciting the lighting, the more your pictures will impress
Stage Dress: Dress for the show and for the photography. Band members wearing wildly differing colors and patterns can come out looking chaotic and disorganized. Colors within a reasonable film temperature range are far more compatible for photography. This does not mean that everyone needs to wear the same colors. The film color temperature for red and green, for example, is very close.
The Crowd: Getting a shot of the entire band is very difficult if friends, fans, and dancers hit the floor the moment the band hits the stage. If you know this will be the case and you want a clean shot of the entire band, you may have to consider doing much of the shoot during sound check. If, on the other hand, you want the crowd included, shots can be taken from the side or from an elevated camera position.