There are really no way to know with men. This my conclusion.
You've all heard your girls swear about their never-fail theory about men's hand-size/dick-size, feet-size/d-size, good-dancer/good-in-bed, good kisser/good in bed.
Seriously, none of these are true. None.
I've been with men who had tiny hands and HUGE cocks, amaaaazing-sensual-making-u-wet-with-his-quiet-yet-assertive-moves in a club, but close to the worse fucks of all time.
And lately, one of the most amazing and deeply sensual kissers i've met in a while.... But really not worth much in bed.
Funny thing is a few of these disappointing performers really think they are the shit. Probably because us-chicks are too nice and we somehow hate to make men feel bad about themselves sexually.
Which adds one: don't trust a man that thinks he's God's gift to women.
Chances really are 50/50.