Mostly pretty straightforward but also 'click' on the player's name in the table (assuming you have the software downloaded & not just doing a player search) & bring up their page. Take a quick look at their results graph to see if they have a positive ROI as a result of one good score (or a couple/few) or if they have a bunch of decent results. Sometimes you'll see someone who has fairly high ROI but are only rated as a Q** (instead of A**, A*****, etc.) & when you take a look at their 'recent high scores' & their graph, you'll see it's because they've typically binked one big score & without it they'd be a losing player.
That's about the only thing I can think of besides the obvious.