Of course we are not talking about following U2 on tour, these are real, hard working bands. The guys (and girls) who do a full day at work in a 9 to 5 then still find the energy to get up there and kick it.
There are two big challenges on these kind of jobs... first off the time constraints. Any photographer knows that for each hour of shooting you have double that to do in editing when you get home. Do the maths, 30 bands... half an hour each... 50-100 photos of each band... that's a lot of editing!
The second challenge is the light, or rather the lack of it. Most of the venues you will find bands like this playing in are by their very nature dark and dingy. This means that the kit lens that came with your £1000 digital camera is useless! Even if you can afford to buy a large aperture auto focus lens the chances are it is not going to do you any good. AF has a nasty habit of not working in low light and of course tends to focus on whatever is closest to you (which is usually a microphone stand!) and at wide apertures there just isn't enough depth of field for this to be a success. Go manual focus, it really is the only way.
So, how do you do it?
1) Practice
2) Get hold of a fast (f1.4 or f1.8) manual focus lens for your camera - I quite often list them on Ebay (http://www.ebay.co.uk/sch/m1roe2)
3) Accept the fact that you are going to push the cameras ISO settings to the limit (at least 1600)
4) Practice more...
5) Get out there and do it, most small bands will be happy to let you in to the gig for free if you give them some photographs to use for promotional material
Gear Used
Canon 50d - full manual ISO 1600 exposure times around 1/30 to 1/100
Manual focus f1.4 50mm prime
Manual focus f2.8 135mm prime