When I have a choice of games to enter, I frequently choose the one with the most laughter. Laughter often means people aren’t playing too seriously. What I hate is silence. That usually means a table full of serious players who won’t enjoy throwing me their money. I avoid such tables unless I’m honing my skills against tough competition just for the practice.
Also I look to see if players lose pots graciously. If players are angry when they lose, that’s a bad sign. I favor opponents who don’t greatly mind losing. These usually are the most profitable opponents, and they add to a congenial atmosphere that makes the whole game more comfortable and beatable.