I've been playing FIFA games since the 2006 World Cup version came out, and when I got FIFA 2012 a few months ago I was also a bit confused at how I was supposed to defend, I used to get scored on so many times that I had to learn to simply score more than my opponent. With experience and practice you'll start getting the hang of defending, what I do now is use L2 like you do, and just get close to the player and if you're close enough the computer will do a little tackle for you.
The problem of pressing O so much is that if you fail the tackle, it's very probably that you will be too slow to get back in position and the opponent will get a wide spot to go forward. Use O as a last resort (when your defenders are running behind the attacker) or when you are certain that there is simply no way that you can miss the tackle. With time you will being to not fail so many tackles lol
The problem of pressing O so much is that if you fail the tackle, it's very probably that you will be too slow to get back in position and the opponent will get a wide spot to go forward. Use O as a last resort (when your defenders are running behind the attacker) or when you are certain that there is simply no way that you can miss the tackle. With time you will being to not fail so many tackles lol