catherine96821:You will certainly go into the situation knowing the issues after reading this thread. Then you must decide your comfort level. If he looks like a disaster then lay down some ground rules for your partnership. If he does not follow then, and you feel endangered, leave him basically. Lets say he is lagging dangerously behind on a site you don't know too well and compromising the dive "plan". You can signal that you are leaving him or you can stay with him, your option.
I would suggest following the "Dennis" rules:
1. Check out the quality of his/her equipment, if really good, stay close, but not close enough to really help. Someone has to retrieve the camera.
2. If it is cheap gear, or stuff you don't want, blow them off as fast as possible and go have a fun dive. Ask them how the dive was, if they make it back.
Plan your dive and dive your plan.