A lot of people say the NDB approach gives them trouble. The hardest part at first is often keeping good situational awareness. If you can picture where you are it'll really help. If you aren't familiar with using a GPS, those approaches can be a little weird at first. VOR's are pretty straight forward. They will all come to you. Practice on flight sim. Call out your altitudes so you don't below through MDA. It's certainly not the real thing, but it'll help you get down procedures...so you don't end up blowing through altitudes on your checkride. I've seen several people do that.