One of the most important things I could ever tell you to help your sex life is to communicate. It doesn't even have to be verbal, it can be written or through video (perhaps watching porn that you like, to show your partner what you want?). Communicating what you desire (and also importantly, what you DON'T desire) is really the only way to be able to ensure your partner can please you in bed. To understand what you want is really a tough thing. Do you masturbate? Can you find pleasure yourself? Showing or explaining to your partner what you like to do to yourself (and having him do the same to you) helps you learn what each other wants, then you can act on that knowledge.
A few things to help you think of things you want: read erotic stories, watch pornography, even read informational things about sex (Talk Sex with Sue is a decent show, she gives some good tips and ideas).
I'm not sure what types of things you have tried or are open to, so it's hard to give actual ideas on things to try. Perhaps try bringing in some toys or food (ice cream, whipped cream, popsicles), or being sexual in different areas (bathroom, kitchen, a car, etc.). Different positions are fun to try (bending over, pushed against a wall, putting a pillow to prop yourself up). You could even try video taping or taking sexy pictures, or using flavored lube or different textured condoms. The list goes on and on!
Sometimes even not having sex can help make sex better. You could both masturbate along side each other. You could play a game where one person masturbates but they can ONLY do/touch what the other person says that they can (like a dirty game of Simon Says). Sometimes even just knowing that you agreed to not have sex makes you want it even more.
Good sex is all about feeling comfortable. Both emotionally and physically. Knowing that your partner understands your needs (or at least tries to) is really half the battle towards doing what you want in the bedroom.
Experience really is a big one as well. With experience normally comes knowledge and ideas. These are things that can make a more well-rounded partner. Even someone who may have experience with mant partners can find it a challange to understand how to please their ONE partner (since we are all different and want different things). So just because sex might not be great now doesn't mean that there is anything stopping it from being fantastic in the future. Keep and open mind and don't be afraid to say stop (or go!). Feel confident in yourself, your partner, and your choices, and that will take you a long way.