Know your limits and your sub's limits.
Try to stretch before being tied up. You will be very sore the next day.
Take 800mg of IB Profen every 4 hours if you happen to be sore the day after being tied or whatever you've been doing.
If you don't think you're comfortable with a certain tie for a certain amount of time, let the rigger know.
Know possible after effects such as bruising, temporary nerve damage, scaring, etc.
Eat before your shoot. There is a possibility that you may pass out between being tied up and having lights on you if you don't.
If bruised, try using arnica cream. It helps the bruising go away quicker.
If urinating in a sub's mouth. It is polite to drink lots of water before hand so it won't taste so strong.
Establish a safety word.
If giving or receiving forced orgasms, I recommend the Hitachi Magic Wand as the appropriate vibrator.
When asked to open your mouth as wide as you can, don't. The wider you can open your mouth, the bigger the ball gag you're going to get.
When being gagged, don't hold in your drool. In bondage, it's sexy to drool.
Start without going over your limits before you begin.
Do an upside down suspension while being gagged if you don't like drool going up your nose and burning it.
Talk back, it's not polite.
Go without the proper lube if inserting any sort of electrical device.
Continue if the safety word has been said.
Continue a session if you are not comfortable with whom you're working with.