I read a nice article about using salt and pepper properly recently. I know this is one area that I've had trouble with (still do actually) and I know I'm not alone in that respect.
Seasoning is tricky because there's no hard rule you can follow and it can essentially make or break a dish. The simple answering is to taste as you go. It's true that tastes vary significantly, but cook to please yourself :).
I like to think of it as a culinary titration.