I have a giant LB button (along with a couple other giant buttons) on my HUD and use it when I know it can and must. It's basically experience you get by doing the content over and over.

The whole Limit Break concept needs a little attention to be honest. Heck, even a rework with smaller personal Limit Breaks available to everyone would be great.
It's not advertised enough and I think it could use a more specific Duty Action button instead of being hidden in the General Category. I won't yell at a new player for not going through all the sections in the Action window and overlooking the incredibly generic LB button.