Sometimes you have to be smart and make him miss. But if you must truck him, the first thing is you have to really believe in yourself and skills as a player. Get lower than him and explode from your legs with your feet under you. If you are not giving it your all then rethink the situation. How big is he compared to you. Watch some old games of THE GREAT JIM BROWN, SWEETNESS WALTER PAYTON, EARL CAMPBELL, and EMMITT SMITH. That should add some pepper to you resume.
It is best to play to your strengths. If you're a power runner, run right at him - low and, pump your legs until you break loose, or you're down. Use this two or three times in a row. Now, he's set up for a juke move that he might not be expecting. And remember this, some guys can just tackle really well. Just try your best and have fun.
This has been more helpful advice from your friendly neighborhood CroppieMan.
Pop Warner rocks!
i teach all my backs foward first, side to side comes with experience. in my opinion trucking is the first thing you gotta learn. most tacklers breakdown before the tackle allowing about a second to make a desicion to make him miss or run through him. when you see that chance, (as if you were throwing a punch), put your shoulder right in his chest and push foward with your legs. you may not run through a great tackler, but as walter payton would say "i'll make him pay for trying". Even small backs in the NFL eventually have to power through holes. and to be honest it hurts alot less if your the one administering big hits and not the defense. If you do it right you'll know when they start trying to arm tackle, that's when you develop side to side. good luck.