Standup pass. Use one hand to hold the belt, (or control the waist if you're doing no gi) so that he can't follow you up and close the distance. Throw your hips forward. Use your free hand to pop the guard (remember to straighten the arm first, don't try to bench press his leg down with your bi's, tri's and shoulders, because that's just a waste of strength).
Once you've popped the guard, connect the elbow of the hand that was on the belt to the knee of that side. That will box out his leg on that side so he can't roll for a sweep.
Use the hand that was on his leg to pin his leg to the ground. Hold him at the knee. That will give you the best leverage. Don't leg go of the knee until your basically in side control. The best way for him to get out is to connect that knee to his elbow and shoot his hips out, and you don't want that.
Once you've pinned his leg, you can step over with either leg for a standard standing, open guard pass.
Hope that was helpful.
The other thing to try if this isn't a traditional BJJ style class is to use neck cranks like can openers and ezekial crank. Those basically force the guard open.
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