If you are a Type A person, someone who can't sit still, or if you are slightly (or completely) ADD, you've got to try Ashtanga Yoga. It's fast paced and follows the same sequence every class, no joke, so you always know what's coming next.
The room is heated (not as brutally hot as Bikram), so your body feels more open and motivated to move. The mats are set up in neat little rows, kind of like your first grade class. The instructor walks around, talks you through each pose, counts the breaths, and assists. Everyone is pretty much moving and breathing at the same time. The energy of the group is really motivating, which is why I prefer going to class instead of practicing on my cold floor solo style.
Fit's tip: Since the instructor isn't demonstrating, you'll have to play "Simon Says" and follow your expert neighbor. Or look for a Beginner class at your local studio or gym. After you've taken a few Ashtanga classes, you'll have it down (dog?)