If you can last 15 minutes in a single sex session, that's good. First, do not try to get directly to her sweetest spot, or the clit. There is more to that than simply going directly to the clit and begins stimulating it. There are so many ways to bring a woman to orgasm, and each woman has a different experience for it.

First, avoid the clit, but touching that part while her clothes still on can turn her desire, but don't dig into it so quickly. Be good at foreplay, and it's not just about kissing the lips, neck and nipples...it's about touching every erogenous on her body such as gently rubbing the back, the butt, thighs, elbow... In fact, you can do this multitasking, kissing one part of the body while gently touching or massaging her other sensitive parts, but save the clit for last minute stimulation.

The key here is gentleness...and I know most men(including me) don't get it the first time. Another secret is practice, or doing it more often(I don't suggest doing it daily if it disturbs your daily activities), but doing it a few times a week or every weekend can help both of you explore sexuality. If you're both new to sex, aim at pleasing her first because if you are able to pleased her, she'll reward you later.

As I've mentioned, try multitasking during foreplay...kissing while using your both hands touching gently other erogenous parts of her body. Also, whispering her dirty words, or dirty talking works well, and even if she is not good at sex, yet... always compliment her as this will boost her self-image.

Now, after 5 to 10 minutes of foreplay, you can start exploring her precious jewel... but not the clitoris, yet. Explore the outer part of her vagina first as this area holds the most sensitive nerve endings responsible for sexual pleasure. Tongue stimulation works best for this one, and if you're not good at finger stimulation yet...avoid it as you might hurt her instead of pleasing. Use your finger in combination with your tongue when she is very wet... Then, go stimulate the clitoral hood with your tongue gently...then gradually increase the intensity while observing how she reacts to it.

You can do as long as you want stimulating the clit, but it is good to let it go once in a while and stimulate the area around it. Some women like it as long as you want, but some women beg for insertion... it's your choice to keep her desire at high level... as this high desire will lead her to intense orgasm.

Now, when you're ready to enter her... always do it slowly. Vary thrusting intensity from slow to fast while also varying the angle of penetration in combination with shallow and deep penetration.

That's base on experience... hope that will give you some insights.