What Is Yoga?: A system that explores the eight limbs outlined in the Yoga Sutra including: restraint, observation, poses, breathing, withdrawal of senses, focus, meditation, and absorption. It is intended to unite mind, body, and spirit, and to achieve a deeper consciousness and ultimately enlightenment.
What Types of Yoga To Choose: There are many many types of yoga all with a different focus. Some are more physical, some are more spiritual, and some are all about spinal alignment. Your best bet is to choose something that fits with your goals and that you feel comfortable doing. The styles below are the ones most commonly found in studios and remember that you can try many and do many. You don't have to stick to one kind.
Anusara - Heart centered practice that focuses on outlook, alignment, and expression through movement. Challenging, fun, and uplifting.
Ashtanga - 6 series of flowing poses and pranayama. Fast, vigorous, and challenging.
Bikram - 26 poses in 100 degree temp to cleanse and purify the body. Demanding, vigorous, and predictable.
Hatha - Catch all phrase for eclectic yoga. Style will vary depending on the instructor so be sure to ask about their focus and level of difficulty.
Iyengar - Focuses on proper alignment and relies heavily on props. Slow and safe. Great for injury rehab.
Jivamukti - Similar to ashtanga but more educational and spiritual with emphasis on readings, chanting, and music. Inspirational, and challenging.
Kundalini - Energy releasing practice with chanting, meditation, and dynamic breathing during poses. Liberating and energizing.
Studio Yoga vs. Yoga DVDs: If you're new to yoga the best way to get into it is to buy a good beginner yoga DVD i.e. Bryan Kest Power Yoga Complete Collection
When To Practice Online Yoga Workouts: After you've been practicing for some time you may experience time conflicts, instructor preferences, expense, etc. You may find that you want to practice more with certain instructors but you can't make their class or you can't afford to do more. This is the time to swtich to at home yoga. A great way to get started with a good dvd collection of one instructor that you really like. My favorite is Shiva Rea.
Practice at home with Shiva Rea: Daily Energy - Vinyasa Flow Yoga

