First off, Yoga as understood by most people is really only a small part of what Yoga really is. In most cases people are either talking about pose work (also known as "Hatha Yoga" in the yoga parlance) or sitting in lotus in an incense filled room, lol (aka "Dhyana" in yoga parlance).

Anyway, there are several popular "styles" of yoga offered today. The following (incomplete list) are just a few that have Hatha work as a large component of what they offer (although this is not to say that they disregard the larger view on Yoga):

• Iyengar yoga. The name of the style is derived off the name of the man, BKS Iyengar, who popularized it. Focues is on the use of props and precision when doing poses.
• Astanga Yoga. Popularized by Sri K. Pattabhi Jois and also goes by the name of Vinyasa or flow style. Here flow or constant movement from one pose to the next is emphasized.
• Bikram Yoga. Popularized by Bikram Choudhury and involves a series of preset poses done in a very hot room.

There are several other forms but the above are perhaps the most popular. My advice for a beginner is to go to a dedicated yoga studio. In general the teachers are more focused on Yoga and are typically certified to some standard before they can teach (although this is not to say that teachers elsewhere may not be certified or for that matter teachers in a Yoga studio are necessarily certified, YMMV). The point of going to a class is to get the basics drilled in but also to have the watchful eye of the teacher to make adjustments which you cannot "see" until you development the necessary body awareness. Also once bad habits are formed they are hard to break. Once you are comfortable in "looking" at yourself then you can self correct where ever you are. To choose a school it is best to go to the school and observe a class or even go to one of their free "open" classes (a lot of studios have this to allow people to try out the style). IMHO, if pose work is what you seek then my recommendation is starting off in a style like Iyengar Yoga which emphasizes precision in pose work, then branching off to other styles to discover more. The grounding you get in Iyengar Yoga, IMHO, is unparalleled.

Good luck.

Following is a list maintained by the respective style on certified teachers around the world:

• Iyengar yoga teachers worldwide list.
• Astanga yoga teachers worldwide list.
• Bikram yoga studios worldwide.