The teacher will use words and will demonstrate. The words explain the basic ideas. It is important to realise right from the beginning that the experience of practising is the real source of understanding. The words are pointers to to the experience or hints on how to adjust the body and mind to encounter the t'ai chi experience.
A vital piece of advice to take on board at the beginning and especially at the more advanced stages, is that when applying a technique it should not be over applied. What does this mean?
When you apply a technique such as sinking the shoulders to empty the chest, when the ch'i does actually sink from the chest it is important to stop applying the technique but to then relax and allow the effect of the technique to continue to manifest in a natural way. The technique is only to kick start a feeling or an affect on the ch'i. If you keep applying the technique after you have achieved the affect it will be counter productive and the result will be blocked. Also you will never move beyond technique and your practice will not become effortless.
When you relax it is important to relax your effort to relax. This is a similar method. It is said that if you think that there is a method then that is not it! This phrase is referring to the application of technique and then the realisation of practice beyond technique.
Whilst this advice risks creating obstacles to progress if you misunderstand, it can be very useful to help become more conscious of the psychological drawbacks of thinking oneself to be student. When you think of yourself as a 'master' you feel more confident and empowered. You do not have to think too much about whether what you are doing is correct. In short, you are able to relax that part of your mind which is too judgmental and robs you of your authentic presence. When applying this approach you will have stronger experiences when you practice.
When practising t'ai chi do not try to isolate your practice. T'ai chi is like daily life, and daily life is like t'ai chi. It may be that you are very relaxed at home drinking tea with your feet up. With respect to your level of relaxation why should t'ai chi be different for your mind? Reflect on the the things you do which you find relaxing and make your mind similar when you do t'ai chi. At the same time pay a little more attention to the subtle things that come to your awareness. Apply a little more concentration.
If you experience emotions whilst practising, this can be the effect of moving your ch'i. Let the emotions come and go without holding on to them especially if they relate to old patterns of responses.