Yep, the main one for the gay scene vanished, unfortunately.
The biggest issue tends to be money. Get the cash before any sexual activity, and you will be doing better than most. For long trips, you want at least your travel money before leaving home. Searching here for 'deposit' will get some tips.
Next is drugs. Have your boundaries in place and, if you're prepared to allow / partake in drug use, then a) don't supply them and b) don't take anything you haven't seen the client take first.
Next is 'I can look after myself'. Make sure someone else knows where you are, who you're with, and when you'll be calling to say everything's ok. (You don't need to tell them about the money side - this is basic good practice, even if not as widely done on the scene as it should be.) Make one of the calls to them with the client around, so they know someone's looking out for you.