No hard and fast rule. Generally for film, I will use either 28-70/2.6 or 24-85/2.8-4 on one body and switch between 18/2.8 and 60/2.8 Micro on another body for wide shots where space is limited and for closeups shots of significant objects respectively. Flash preferably you use a bounce card but I have resorted to using the Lumiquest Softbox.
Most important is to stay alert. Watch your foregrounds and background. If it's a group shot, remember you're the one calling the shots and arrange your subjects. Anticipate what's going to happen next (experience quite important here) and be prepared for it. Also, watch your frame counter, if you have hit 32 and you have some time and don't know what's going to come up next, just rewind and load a new roll first.