contesting shots and blocking

hey i just got xbox live. I play on allstar and i can usualy block shots wit big guys but on xbox live the other people are blocking every shot with every player and when i go for dunks they do wut i thought only the computer could do by conetesting shots and usulay causing me 2 get a charge or mis layups/dunks so i gess my question is how do u conetest shots when they go for dunks and how do you block with out fouling?? thanks for help
P.S i have looked all over the internet for this
oh yah 1 more question how do u allyopp 2 urself in 1-1/practis

Use the off-ball switch in 1-1, practice and the all-star game. Rookie/soph game, too, I think.

-JKidd