at the very least, always go through a lost buddy procedure plan and make sure you both agree on it (and stick to it) - sometimes new buddies like to wander off and don't really pay attention to where you are, sometimes you have to be the better buddy and just try to follow them where they go... it sucks when this happens so if it is a two tank dive and you notice this on the first dive, talk to them about it. Otherwise, it is also nice to know how many dives they have done to kind of gauge their true experience level etc. compared to yours.