I would say show off your most attractive parts: If you have a 6 Pack, show if off, if you have a nice smile, show it off.
Some guys put a picture of their pet in their profile- stoopid. I wanna see YOU, not your pet.
Another BIG mistake: A picture with your ex. NEVER ever put a picture of you with another girl besides you in your profile.
Same goes for you and a bunch of friends, maybe out in a bar or club.
Even if you look handsome in the picture, it will come across as........dunno, like all you do is party and drink.
And no picture with a drink/beer in your hand either or you smoking a cigarette.
Just you, your nice smile or nice abs.