Yoga Which Kind??

Try different classes in the area. Like the other poster said, a lot of instructors will let you do a free drop in to get a feel for the place. I do hatha yoga with a teacher that actually instructs. Most of the teachers in the area do their own practice in front of the class. I found that frustrating. This instructor asks about a health history and will tell you to do something different if a pose isn't good for your body (ie you are pregnant, or have a shoulder or back issue). Most good teachers have done either 200 or 500 hour teacher certifications. A lot of teachers just do a weekend certification thing (ie 15-20 hours) and then start teaching. I recommend the teacher who did the 200-500 hour training. Our teacher goes a 10 minute meditation at the end of the class and also instructs us on breathing during poses.

hth!

What you can do is:
Many places will let you take a free try-out class.
Or, talk to the Instructor. And ask them.
Or, rent some Yoga videos, and try it out. That way you are trying it out in your own home and comfort. There are many kinds.

Also, per your need for stress/relaxation... there is also, meditation, and "deep breathing". My Mom actually took a class on deep breathing, and it really helped her per her own stress and reduction of it and it has many other health benefits too.
Look up "deep breathing" online.
Meditation and deep breathing, has actual clinical based results.

The last class I took was Bikram. It is for athletes or for people who are willing to sit out for part of the class while they catch their breath-lol, it's pretty intense! It is a type of "hot" yoga where the room temperature is up over 100, but the same exact routine is taught in every class. Class is long-1.5 hours. You will sweat profusely. PROFUSELY. I could actually hear sweat dropping from the shorts of the guy in front of me, and it was pretty gnarly. Pros: It's an AWESOME workout. Members tend to motivate and support each other. It's probably unlike any workout you've ever done before.
Cons: some of the Bikram instructors are militant. FOr instance, some of them only let you drink your water in between certain poses. I once got scolded for taking a sip at the wrong time. They like you to keep your eyes open at all times (sometimes I like to close my eyes when I stretch-got scolded for that too!) They are nit-picky about form as well, but if you're a newbie they will cut you some slack.

In my home I occasionally do Vinyasa, preferably to a Rodney Yee DVD. I like Vinyasa because you just move from one pose to the next, to the next, without holding the pose for an extended period of time. You hold each one for maybe 4 breaths. All that movement provides a gentle aerobic workout and you become familiar with a lot of different poses and series. ONce you learn a particular series of flowing poses you can do them on your own without the DVD, wherever you want. I believe Ashtanga and Power yoga are the same as vinyasa, but I could be wrong.

In college I tried Hatha Yoga. If I remember correctly the focus was more on holding poses, achieving the best possible form, etc. I found it to be boring, but many people love it.

Hopefully that was helpful

If you go to your local library you can check out all kinds of Yoga DVDs that have all different levels and benefits: weight loss, stress relief, digestion, etc. Plus its all free.
If you are looking to build muscle, you may want to try pilates. It helps create long and lean muscles without bulking up, just adds good definition. And always do some cardio and stregth training as well.

I do 3 different kinds, One is a hybrid style that involves aerobics, One is a slow moving official kind of yoga that focuses on perfect positioning and relaxation. The other is prenatal yoga (borrrrring)

If you have netflix, put some on your queue and try them out