I have been practicing yoga and meditation for many years and have friends that I have met through my various yoga adventures that started out as mere yoga students like myself who now own and operate their own yoga studios.  I have never had such aspirations as my yoga skills have remained at the beginner level despite my years of practice, but there may be others out there who are interested in transitioning from yoga student to yoga teacher. Typical requirements are that you have practiced for several years, can do a headstand in the middle of the room, and have taken some classes with the teacher you propose to train with.  Here is some valuable information from About.com on requirements of becoming a certified yoga instructor and some tips for finding the right studio to train.

In the United States, teacher-training programs that meet certain standards are registered by the Yoga Alliance, a nationally recognized organization. There are two levels of Yoga Alliance certificates- 200 Hour and 500 Hour, referring to the length of the program. Trainees first complete a 200-Hour program, which most yoga studios require as the minimum training for their teachers. Some teachers then choose to continue their studies by undertaking a 500-Hour training.

When looking for a training center it may be best to start at your favorite yoga center.  Many yoga studios offer teacher-training programs, but take a good look at the curriculum before you sign on. With trainees paying thousands of dollars in tuition, yoga teacher training has become a moneymaking operation. So make sure any program you consider is Yoga Alliance certified. This will guarantee that your certificate will be of value when you are finished, and also that you will spend a specified number of hours studying asana, teaching technique, anatomy, and philosophy.  The most important thing is that you feel comfortable with the head instructor, as you will be spending a lot of time with them.

Related Reading:

The Yoga Sutras of Patanjali: Commentary on the Raja Yoga Sutras by Sri Swami Satchidananda

The Encyclopedia of Mind, Body, Spirit: The Ultimate Guide to Healing Therapies, Esoteric Wisdom, and Spiritual Traditions

Yoga Philosophy; Lectures Delivered in New York, Winter of 1895-6

Yoga Pretzels (Yoga Cards)

The Spiritual Guide to New York: Yoga, Buddhism, Wicca, Kabbalah and Beyond