This is a very simple and effective Half Guard Pass. It works well as a beginner and continues to be effective all the way through the ranks.
One of the great things about this pass is it does not require a lot of hip movement, balance or strength. As long as you understand how the leverage is applied by "caterpillaring" your body down your opponents legs (reference the video).
Make sure that when you make space for your hand under the legs you do not over commit yourself to pushing into your opponent. The amount of force to it takes to makes this small bit of space is not a lot.
Once you have broken open the legs there are hundreds of possibilities. I prefer to maintain control of the legs by initially flattening out and then by having an intense driving pressure of my shoulder into his/her body.
For added control reference the video for the way that I control the legs. I have not seen a lot of people control the legs this way and it may be something that you want to try out.