Some great advice already, as others have said the earplugs are essential. I spent too much time not wearing any and I really regret it now, you only get one pair of ears. Plus there is a big chance your average pet rabbit has more musical talent than some of the 'artisits' so they are helpful with just being able to block out the god awful noise.
I had a venue and we often had bands, especially at showcase events they tended to be younger, and they usually think they are hours away from being the next big thing. The good thing about a showcase is they want the photos, so they won't mind what you do to get them. If you need flash use it, if you need to crawl around on the stage then do (you should, it makes for good pics), but be aware some may well be drunk when they arrive and very drunk by the time they get on stage, add in the ego element and the adrenaline and you sadly get idiots. Just watch your camera basically. Usually I got hassle from their friends and family, they get mouthy and think they are related to the next big thing, I've probably kicked out more of those people than I ever kicked out drunk and aggressive punters!
We had one event on a Sunday, bands arrived at 9am, it was daytime as it was for filming and sound recording purposes. One band rolled in and the drummer, if he was 18 I'd be very surprised had a can of special brew he was trying to drink but blatantly hating, he had an unsmoked rollup slowly burning away at his fingers, he was wearing a vest and had his one token starter tattoo on his arm. It was the middle of January and we were all wearing coats inside as it took a long time for the heating to warm the big room. He tried to be the hard man when I told him to go outside to smoke and leave his beer out there too, I really didn't think I'd be manhandling drunk 'rockstars' at breakfast time on a Sunday morning, but his mates told him off and he waddled off, jeans round his knees nearly. When they played I think he hit the snare only, with the occasional kick on the bass drum, he was about as talented as a goldfish. Halfway through their set the organiser had a few words with various people and he was asked to leave the stage and replaced by a drummer from another band. His face was a picture - would have looked great on the cover of Kerrang!
I'm not saying it's a bad thing to do, I quite enjoyed some of the nights but then I tended to work with agents who were putting on acoustic acts, vocalists, anything but rock and thrash metal really! We did those too, but they were a bit messy. You may find your event isn't full of bands trying to make as much noise as possible with as much talent as a toilet brush and instead has some really nice vocal artists and lovely people who really appreciate the evening, if that's the case it does make it all easier. I never photographed them, I sometimes managed the sound and lighting, and if the photographers asked for certain lights to be changed I always would if I could - afterall we were being paid to help them showcase, no point in annoying anyone. The artists on the whole were lovely and grateful, it's just the noisy nights with the alcohol fuelled metal kiddies we didn't enjoy and would avoid if possible. Bless their cotton socks.
