If you are a beginner to yoga and have just decided which class you're taking first, you'll be faced with the question that haunts many of our teenage memories: what am I going to wear? Allow me to allay your fears. Yoga class is not a fashion show. You can wear whatever you feel comfortable moving your body in.
It is important that you feel supported, your limbs are unrestricted, and that you can breathe easily. So while there are never wrong decisions, it may be an ill-advised choice to wear a turtleneck and tight jeans to a hot yoga class. In general, shorts, yoga pants, t-shirts, loose-fitting clothes, and supportive under garments are always a safe bet. Certain yoga classes may require slightly different clothing choices. If you are taking a class where posture alignment is a high priority, it may be helpful to wear more closefitting clothing. This will allow your yoga instructor see the positioning of your body and help adjust your alignment. If you are taking a hot Bikram yoga class, you may want to opt for shorts as opposed to pants. Another wise decision is to dress in comfortable layers so you can add or remove clothing if the studio is cold or warm.
In terms of footwear, most yoga classes require you to leave your shoes outside of the studio, so most yoga students are barefoot. Some people prefer to wear socks into the studio and then remove them before the class begins. Others choose to wear "yoga socks" that have gripped bottoms and individual toes. If you decide to wear socks during your yoga class, it's important that they have grips on the bottom so you won't slide on your mat.
When you attend your first yoga class, you will see that people wear a variety of different types of clothes. As with all things yoga, clothing is a personal choice and varies from person to person. Whatever feels best and makes you most comfortable for class is probably the right choice for you.
Resources: http://www.gekkos.eu/ http://ezinearticles.com/?Beginner-Yoga--Dressing-for-Class&id=5046904