Humans are perhaps the only animals in whom sex is a learned behavior and sadly very few learn it right in the first place.
Here are a few random “right start-up” tips which I can think of… …
The most important ingredient for repeated good sex with the same partner is LOVE.
The second most important ingredient is COMMUNICATION – in short ASK
The third ingredient is de-focus the act from COITUS – there much more to it than “wham bham thank you ma’am”
Planned sex is just as good as spontaneous sex, and what follows as a corollary is no sex != no love.
If it hurts – you are not doing it right.
Forget G spot, search out Y spots (Spots which make him/her wonder why are you doing it
Be innovative – a personal fav is the game of “No Touch” – Think what it could be!
Lastly if you really need help – get a good book which tells you how, like “The Complete Idiot’s Guide to Amazing Sex