There are many styles of t'ai chi as well as methods of teaching. Choosing a teacher is an important first step.
Also important to know is that t'ai chi is learned in stages. Your teacher will guide you through them properly. Ignoring these stages of learning will only result in a lot of wasted effort.
And perhaps most important, it is critical when starting out to develop the right study habits. In the beginning great emphasis is placed upon learning each posture correctly. This kind of exact learning requires repetition, time, patience, and effort.
Yang Ch'eng-fu, whose style of t'ai chi I practice, admonished students when beginning absolutely to avoid haste.
"And while you may not remember me, I well remember you, and I just want to thank you for introducing me to T'ai Chi and starting me on this amazing journey."
— Staara, Indiana