Best tip - listen to the DJ you are being a roadie for!
In all honesty, the only thing to keep in mind is... mind your please and thank-you (you are, after all a form of representative of the service) don't get drunk, try to pick up someone's girlfriend / wife or start a fight and throw chicken legs or disco equipment at anyone.
Leave that to the DJ.

Just be mindful of the things that the dj will not be able to keep their eyes on, including health and safety, such as when there is a lively crowd who are edging towards the gear when dancing. Nobody wants the fun to stop, and likewise, nobody wants to have to pick a clump of scalp or flesh out of the gear if they've fallen on the rig.
If the DJ has any business cards, he / she may appreciate that you pass on if there are requests for a card but other than that, I'd keep an open mind as every gig is different and after attending a few gigs, you'll get the experience / idea.
Oh, and don't wear white socks!
Have fun.

dont go with the daughter before he gets payed.