I might be alone on this, but I really think the most passionate kisses don't involve lots of tounge. Instead, try making the kiss a whole body affair.
If your standing:
Like the above poster mentioned, I LOVE to use my hands while kissing. I will place my palm somewhat under her jaw with my fingers just below the ear... that way I can draw her into me with my fingertips. I like to gentley touch lips and massage where her lips would touch, if her mouth was closed, with my tounge. (make sure you lick your lips slightly before kissing) While we're kissing I will stroke her cheek with my thumb. With my free hand I lightly touch the small of her back (some times I will move my hand to her hip to draw her into me... this is usually when it gets a little steamier).
If your lying down (male on top):
I like the same as above where it comes to the actuall kiss. Where it differs is with the hands. A line from a John Mayer song always comes to mind... something like: "I'll never let your head hit the bed, without my hand behind it". If you're on top, hold her like she's precious to you when you kiss. One hand behind the head and one either behind her shoulder blades or under the small of her back.
One bit of advice: Woman usually have smaller mouths then men do. What's comfortable for you will most likley not be that comfortable for her. Follow her lead when it comes to how far open your mouth is.
Take it slow, kissing is not a tounge-lap-race. Usually, the slower the better.
Make sure you're not drooling on her. I salavate (sp?) quite a bit and have to be carefull abou this, especially when I'm on top.
In between breaths, it's nice to tell her how you feel about her or say things like "you smell wonderfull", "you're so beautiful", I've missed you so much"...
Most of all, enjoy yourself.
[posting this really makes me wish I had someone to kiss in 40 minutes for newyears...
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