If you begin to feel uncomfortable, motion to your yoga teacher to help improve your pose. A good yoga teacher will tell you to back out of a pose if it's causing you great pain and discomfort. Remember, yoga isn't about stretching your limits immediately; it is a gradual, healing process.
The usual lightweight clothing, anti-sweat athletic wear that dries quickly will do just great. For men its light tees with shorts and women can wear a tank top or sports bra with shorts or lightweight pilates memphis yoga-style pants.
It might take you some time before you are able to perform the positions well. Don't be discouraged by your lack of coordination in the beginning. You will find yourself unable to reach the correct position or when you do it cannot be held for very long. This is a normal part of learning to practice yoga. It takes a great deal of time before you are able to do the stretches and positions with the same kind of grace and ease that you see from yoga experts. Watching others can be a little deceptive. Some yoga experts make the positions look effortless and you will soon discover that they are anything but effortless.
There are more people enjoying Bikram yoga because it can help people get exercise, but it also release toxins from the body. It's done in a heated room, which means people sweat in excess amounts. A big Bikram mind body haus mat is needed to handle all of the moisture.
In the 1980's, Dr. Dean Ornish linked hot yoga and physical health together when he suggested the practice of yoga for attaining a strong and healthy heart.
If you're concerned about not being able to perform some of the poses, don't worry. Most poses have varying degrees of difficulty and can be easily modified for beginners. Often, the instructor will be available to show examples of modified poses and to help you get into proper position.