Blocking is essentially wanting it more than the defender does. Stay low and balanced in your hips, get your feet wide, use short choppy steps, NEVER stop your feet, extend your arms, get your hands inside, and grab cloth.
Tackling is just the same except you get your arms behind you, shoot your hands and hips at the same time, wrap your arms around the defender, grab high cloth (near the helmet), and always get your head in front of the defender.
In football, ALWAYS ALWAYS ALWAYS see what you hit. Never put your head down to hit someone. Doing that is illegal, and it is a great way to break your own neck.
