Be honest, positive and demonstrative
If you're going to say what you'd like and ask what your partner wants, there are three important points to keep in mind.
Be positive. Don't tell your partner they're terrible in bed. Remember something they did that you really liked and say, "When you did that, I really..." They'll get the message.
Be honest. There's no point in faking it or saying you like something you don't, because that gives your partner no incentive and no guidance to do better.
Be demonstrative.
Erogenous zones
The most sensitive sexual areas are
Breasts, nipples, genitals and lips
Ear lobes, fingers, toes
The soft skin inside the elbows and knees, the small of the back and the nape of the neck