Good luck! Principal photography is great fun.
Though a couple of tips I would offer from my own experience:
- Make sure you have everything at the ready beforehand: battery charge, setting, timings, script etc.
- If you're working with friends, who are doing it for free, then make sure you don't treat them too harshly. Most of the time, you do get the odd friend/s who begin to mess about a bit; if so, either try to do as much little work with them as possible or somehow talk sense into them.
- And make sure you either have food and drink at the ready, or organise a time slot for a trip to the local shop.
- And best of all, just have fun!