So, in this technique is quite important to know. Is like a basic form the half-guard (I am not very good from half-guard though ://). Very important is to really lock his leg with your "free leg" and grab the back of your opponent really tightly. If your opponent manage to avoid the first sweep (which most people with some BJJ experience do), then the second sweep is very useful and works very well (see the clip at 2:10 approx to see the second technique).
Here is the third technique.
A little bit more unusual and I have actually never had to use it. But might be good to know, you could bait your opponent to go to that position.