Get her all worked up, while making out is a great way to do this. Start kissing her down her neck-this is called necking- and slide your hand down her stomach and stick just the tips of your fingers under her waistband, leave them their for a few seconds so that you wont surprise her and have her freak out. Watch her reposnse at this point, if it is positive or negative, if positive go back to kissing the mouth, if negative you may want to reconsider. If she asks you waht you are doing try something like "i wanna make you feel good" with a trusting look on you face , then slowly kiss her again. Once you have gotten into her pants, literally, DO NOT go straight for pussy, even if she is not wearing any underware, rub your hand over her pussy for a while, try to get the sides and avoid the middle, this will let suspese build. Make sure you do this over her panties/thorng if she is wearing one. Once this is done slowly slide your hand under her underware, removing pants as needed, and do the cunt rubbing thing again, stay away from the middle. Start discreetly feeling for her clit, it should feel like a little fleshy nub near the top, you may have to move some lip out of the way. From here you have two ways to proceed
Rub her clit, this will make her cum, try to get some jucies on your finger, it will make things easier, watch how she responds since everyone ahs thier own preferance.
Go for the G-spot, if this is your or her first time dont do this. The G-spot is located about 2 inchs inside and is on the side facing you, use your index finger to stroke it, dont stay over it forever, try to put in a second finger, some like it and some dont, it you really want to drive her wild rub her clit with your thumb while you use you other fingers on her clit.
after she cums dont keep on going, but dont stop until she is done. The purpose of fingering is NOT to simulate sex but to just stimulate her in general. Some guys will recommend a finger in or pressing against the ass, she will either really like it or think you are a pervert, do so at your own risk.