Always add at least 4 feet to what you think you need.
If in doubt, on carpet, double lay it,
If your dolly's not working right, call the company. Make them figure it out.
Under 50 mm, you're probably fine. Over 50 mm, use skates.* See the update below.
When in doubt, call for it ( I know the guys are tired. I'm tired too) Don't be afraid to call for what you need. Even at the end of a 16 hour day.
Above all else, make your operator comfortable. It will get you jobs in the future. And it's your job.
KNOW YOUR EYELINES.
Don't be afraid to say "No" if something's dangerous. It's not worth your career or someone's life.
The eyepiece is always on the left. (Most of you know what I mean).
Know your heads (O'Connor etc).
Always mark the front wheel.
Keep the tanks full. Running out of juice before a big move is a novice move. It has happened to all of us, but keep an eye on your pressure.
An O'Connor head is 14" from base to lens. Factor it in.
A monitor will not make you a good Dolly Grip.
*Update- I wrote this when I was primarily using steel track. It's nearly impossible to get decent steel track anymore and when I wrote this it was true (and still is for steel). Generally, any of the aluminum I-beam tracks, GI Track, FilmAir, etc are good enough that you may only rarely have to use skates anymore.