I don't know how tall you are but I'm 6'2" and I think sitting is the best position anyways. I prefer to sit down normal, and she sits facing me on top of me, with her legs wrapped around me. It is a bit difficult to explain but thats what I like, and she likes it too. During a make out session I normally change between three positions, that sitting position, laying down with her on top, and laying down with me on top.
You don't know where to move your hands? Easiest question ever. Everywhere. Especially if she's wearing shorts. Mmmmmm. Run your hands up and down those silky smooth legs, inner thighs. Run your hands up and down her sides, gently run your fingertips up and down her back, caress her neck, run your fingers through her hair, and then gently stroke her cheak with your hand.
Take a break from kissing her lips and kiss every inch of her body. Tease her. Lick your way up her thigh and blow on it. Raise up her shirt and kiss her bellybutton.
And remember its all about having fun. Be playful sometimes. Tickle her here and there. Tickle her here and there...with your tongue.
Tease her. Be very intense for a few seconds, with a very passionate kiss and rubbing her ass and her breasts. Then stop like something is wrong. If she asks whats wrong, maybe smirk a little and say nothing, then go right back to it. Do it over and over again until she is practically dying for you to rip her shirt off.
Let her be the teaser. If she follows your lead and starts kissing around, don't let her get back to your lips. Let her kiss your cheek, and when she tries to go back, smile and turn your head away. Maybe feign disinterest. I had my girl repeatedly telling me, "You can't resist me. You know you want me." When I did this.
You lucked out, my girlfriend just left so I could basically write about everything we did fresh from memory.
Unfortunately things took a turn for the worst (not either of our faults), I might post about it in a little bit.