There are things that you ought to do before, during and after every Tai Chi session. They are called precautions. Well, this wont be new to you because almost all exercises have certain precautions that every practitioner must observe and follow.
Below are some pointers to ponder on (for beginners and those who have medical problems):
Precaution #1
Never attempt to learn Tai Chi through instruction manuals and online videos. The book can only tell you what to do and what are the basic principles behind every move but it will not actually exhibit the right or wrong positions. Trying to imitate the Tai Chi DVDs can be quite a hag.
They will make you want to try and learn but will be very hard for you to keep on pushing the stop-rewind-play-stop-rewind-play-fast forward buttons just to catch up on their instructions. Things like this will never tell you if you have made a mistake in your performance. They will just go on and on. Besides, if you have a particular question in mind, your manuals and videos will not make the slightest effort to answer you.
It is always safe to learn from someone who is experienced enoughed to teach you, PERSONALLY,...