Based on my experience, don’t try to shoot anything after the first three unless you get explicit permission from the venue. I’ve seen venue policies change and privileges removed for all photographers due to one example of a photog not respecting the rules.
Shoot with the fastest lenses you own. Respect the crowd but the pit is your space for those three songs. Respect the space of the other photogs. Don’t lift your camera in the air in front of other photogs. Don’t use flash unless it’s explicitly allowed. Don’t bump into other photogs while they are shooting.
The types of shots you want to get depend largely on the lenses you are bringing. But try to get a balance of individual shots and group shots, tight and wide angles, action, facial expressions, etc. avoid mic stands in artists’ faces.
Those bands are big enough to play venues that hopefully have decent lighting, which should help you.
Also, make sure you enjoy the experience. Shooting concerts is a lot of fun. After the three songs, hopefully you can put your camera away and enjoy the rest of the concert as a fan.
Who are you shooting for? The band, a publication, a wire service, something else?