If using a dolly always bring some cardboard as a substitute for tracks if you don't have any
When working with people not familiar with filmmaking always bring something like ice blocks or hot chocolates/coffee depending on the weather
Take frequent 5-10 minute breaks
Bring several spare battery's! You Will need them!
Bring along someone who can hold a light reflector or diffuser so you can (quite literally) "focus" on focusing your image if it dosent to it automatically. (manual focus is recommended)
BRING EVERYTHING YOU COULD POSSIBLE NEED! For an example I was shooting videos indoors and you wouldn't expect that you would need a polariser but my UV filter was creating a bit of glare on the lens so if I had a polariser I could of fixed that and got a better image!
Protect your gear! Make sure you keep (your camera especially) your equipment cool if it gets to hot some things like your battery will drain faster.
Take a wide shot of your sequence and watch it play out, then you can decide on the intimate camera shots and angles or pans whatever you feel will look the best
Evaluate your shot and use the rule of thirds
Shoot your scene in a wide as your "master shot" so when editing you can always cut to that wide if you need to.
Experiment with different angles.
The positioning of the light of a person can change the viewers perception of the character. E.g. If your actor had soft light from a diffuser falling on him it's allot more flattering and the actor wouldn't look threatening whereas if your actor had hard light creating harsh shadows on his face he might look a bit more threatening and scary.