ankle taps and tackles

I am playing in the franchise mode (trying to get some practice in-keep getting whallopped online) and the computer ankle taps me all the time. I have tried endlessly to do it myself but to little availe. I play on the ps3 anyone know how to do this.
Also whats the best way to tackle to stop players breaking past you. For example when your trying to bring down Jacobs out wide-he just brushes off defenders for fun.

Push right stick down for tackling the legs, thats what you wanna do against a big guy like Brandon Jacobs. But still Trucking is way too overpowered atm, they break too many tackles and when they get out of the 4vs1 pile you just go lol...

If you press right stick up its big hit, but this is alot harder to get an actual tackle with in this years game, you gotta get the angle right