By actions and abilities they've shown, and competency shown for the game and it's mechanics. Being around average at best myself, I feel like I make a good middle ground from which to judge other players abilities. If they can best me, and there are no extenuating circumstances such as bad luck or poor timing, and I was giving my best, I will rate that player mentally as a rather high 7+/10. I'm more of a 5 or 6. On the flip side, if they can not seem to connect shots or simply can't seem to control their character effectively, then they receive a 3 or 4. 1 and 2 are reserved for only the most incompetent players, such as those who consistently fail due to their own actions, or lack thereof. I try to be fair, a person who gets lucky consistently might actually just appear to be that good of a player, other times people just have good games, or good days, and the opposite is also true. Taking these variables into account, and try to understand that sometimes I am wrong, and fully admit so, I find that a player such as Mtashed, KJHovey, TRIPLEwreck, or, can't believe I'm saying this, Shesmynerd, would scale 9 and 10, where as a player similar to my friend Hero, who is reckless and aggressive, scores about a 3. =) BEHOLD, THE JUDGEMENT-TRON-9000!!!! A.k.a meh brainz. =)