this was probably posted a while ago, but heres my opinion,
usually i find the best bjj and grappling practitionists prefere to use the butterfly gaurd, but when im in my opositions closed gaurd, i tend to try and stand up and go for leg locks,
then again onother technique that always work for me is to stick a knee up their ass, turn the hips and put pressure on one leg to break the gaud, you have to slide over their leg pressing your shin into their thigh so you dont get caught in half gaurd. alternativly use your elbows and put pressure into your oponents thighs, very uncomftable for them and they usually open the guard and try for another possition.