There's drills, but they're difficult to explain. I'll give a few a try.
Lay on your back. Lift your legs up like someone's in your guard or something. Now windmill your legs, mostly below the knees. Do it fairly quickly. Reverse directions. Mix it up a bit. The idea is that you are blocking out an opponents arms as they try to pass your guard.
You're a wrestler? Lay on your back. Bridge (you've just bridged someone off of you). Roll to your stomach (imagine your now in side mount), switch to kesa gatame position (
www.judoinfo.com ), flop back onto your back and repeat about 25 each side.
Lay on your stomach. Prop up on your foreamrs and toes. Only your forearms and toes (well, balls of your feet) should be touching. Scissor your leg to the right into the kesa gatame position. Pop back to the forearms, toes position. Now kesa gatame to the left. Then back to the forearms, toes. Keep going for a long time.
Shrimp. Shrimp backwards across your room. When you reach the wall, shrimp foward across the room.
Roll. Literally. Just roll around on your floor, from kneeling, foward rolls and backward rolls. Get a flow going and do it for a couple minutes.
There's a bazillion drills, these are just a few.