Obviously the guy (I'd never learn MA from a girl) should be in good shape and able to execute all techniques with a very high level of proficiency. Your age also will determine the style best suited to you, if you're older you'll probably want to stick with a style which emphasizes hand strikes and low kicks (to the knee, etc.), like 1 of the Kung Fu styles. I took Shaolin for a brief period (6 months) and I really enjoyed learning and practicing all the varied hand techniques and different stances. One thing I personally found fascinating was that all of their lower forms blend together as you rise in rank, the lowest merges into the next and so on. When you get to the highest rank you have 1 long form composed of all the others. Very cool. You can't go wrong studying martial arts .... you just have to find a legit school.