(A/N: we're just going to assume you already are dating cause the stuff that cones after is where the fun REALLY starts.)
Leo: in public around his brothers he doesn't usually kiss you, but when he does its on the hand. He likes to be a gentleman and hold back his true feelings, but at night when everyone else is sleeping, that's when the gloves come off. He likes to kiss your neck when no one's around.
Raph: Raph doesn't really care whos around as long as it's not soft, like on the ear or top of the head. He is more rough when it comes to kissing around other people. ESPECIALLY his brothers. But when you two are alone, he's the biggest softy and very sweet. He tries to control himself too, but with a big guy like him, he sometimes loses control (a wank wank ;) )
Donnie: oh, Donnie-boy. Donnie LOVES to kiss you on your thighs when you two are alone. He is just all OVER you. He can't keep his hands off you when your alone. But in public he'll kiss your lips softly. Only in his lab with he lift you up, place you on his lab table and have quite the make-out session with you. Oh, Donnie ;).
Mikey: Mikey is VERY adventurous. So when you two kiss its a whole other level of hot. He'll kiss you anywhere from the top of your head to your 10 little piggies. He loves you and doesn't stop exploring your seas. ;)