Do you go by your eyeball test in watching games? Watch replays/tape? Go by or, add in stats? Rate on a curve based on other players you have seen or seen stats? Go by or, add in value based on cap costs? Go by or, add in what analysts have said? Something else?
Interesting question with many options for answers.
Eyeball test, 1st and foremost, then health/will to play/heart, finally check stats to actually see how the player handles situations you might have not been aware of.
Basically, stats can lie, but if you are watching the games, and paying attention, you are getting the most honest look of what type of player he is.
After that, how tough is he, is he injury prone, is he willing to put in the time to get better. I put all these together because it is important to have a player that is physically and mentally ready for what the NFL will bring each week, if he is not, I don't care if he is 6'9 380 pounds, and can run a 4.2 40...he will fail.
Finally the stats will give you further info, of how the player did at certain moments that you may not be aware as, consider when you are watching a player, you are watching him as a whole, not in certain situation.