After you get comfortable with this, you can begin playing with different techniques. The G-spot, also known as the Grafenberg spot, is an actual location in the vagina just on the other side of the urethra, and all it appears to be is a fibrous bundle of tissue. No one is exactly sure what it is for. This research has not been replicated by any other major institution, and after 20 years of looking, there is no information proving this. It is possible women get some kind of pleasure from G-spot stimulation but most don't.
Clitoral stimulation is the most common source of female orgasm.
Self-esteem is something you need to work on. How you feel about yourself is conveyed to people. Focus on the things you are good and bad at and get to a place of acceptance about who you are and about what cards of life you have been dealt. If you find you tend to be self-deprecating, then you might be talking people out of liking you. A neat place to practice for shy or self-deprecating people is in free form chat rooms so you can experiment.