Tips and "How-To" for Evaluating a Potential New Roommate?

Soooooooo my situation is this. I am considering moving into a new place with a good friend of mine whom I trust highly AND his friend whom I have only ever met once. My good friend has known him awhile but says he has within the last 6 months gotten closer to him and this prompted the situation for us 3 to move in to a place together.

Like I said I trust my friend and upon the few interactions I’ve had with the new guy everything seemed fine. But we were supposed to check out a place together and the new guy is getting flustered and annoyed over the fact that the landlord hasn’t returned our initial call to show us the place today. If the LL isn’t available they’re not available, what can you do about that? Red flag.

My question is what are some things I should look for based on very limited interaction as other potential red flags? Also do you think I am overreacting and wrong to assume that his behavior could potentially affect me negatively?