I have another tip, pretty quick if you have PT and are playing a reg. Simply check their position stats and see if they play position, and if they do, whether they focus on just the button or have a nice, solid upwards curve of aggression. There is a massive difference between a 20/15 playing 10% UTG and 30% on the button and playing 15% on both, and it hugely increases the information available to you.

(similarly, do they play too much from the blinds, another useful thing to know)