Don't keep the light on all the time just have a quick scan round till you spot something, when you do get yourself between it and where it wants to run to then stick the lamp back on and either slip the dog or walk it up if its a squatter and the dog doesn't know to run the beam yet. As for technique you'll work out your own, everyone lamps differently but try and get yourself between the quarry and its escape route.
Edited to add, keep the lamp on the rabbit not the dog or infront or behind the rabbit. Sounds daft but some people do it.
Good luck.