It basically consists in a lot of practice, Alkramoz.
My advice would be to play around frequently in Free Play, using 0 0 -30 gravity (it's the one that's commonly used for realistic purposes as opposed to 0 0 -9.82), at least a bit everyday.
Realism (and consequently sparring) usually comes later in. Starting to go that way on your first month of playing might be too rushed, but if you're persistent enough, go ahead and have fun. Just remember that we all failed a lot in order to become better.