I found that small gravel or dirt (like a baseball diamond) was the best surface for learning to skid.

Re: the original question:

The lower the ratio, the easier it will be to skid, but assuming your ratio isnt ridiculous, you should be able to do it. Practice riding around with as much weight on the bars as possible. "Balls to stem" is a good way to think about it. As you get better and stronger, you can shift you weight backwards more and stop faster.