If it's just the first kiss, stick with a nice lingering kiss with no tounge. Just lean in slowly and close your eyes. Not terribly hard.
Later on when you're making out, you need to vary things. If you're making out for 20 minutes or more, things can get boring if you don't use your hands and change angles and kiss on different spots. I like kissing my girlfriend's neck because it really seems to turn her on. You should start off with a normal kiss with your lips slightly parted and then part her lips with your tounge. You should vary the speed that you kiss and movement of your tounge. Don't dart it in and out or leave it in her mouth and not move it around. When taking it slow, grip her nice and softly around the waist or small of her back. When things start heating up and getting amped, I usually grab her a little firmer around the body or reach up and pull her face to mine and tug the back of her hair a bit.
But it's all up to you. It's pretty self-explanatory once you get to it. It's easy to tell what makes her feel good and doesn't. Also, don't slobber all over her. It's just disgusting.
The only way to get better is practice. So go get a girl and practice.