Try asking these 10 metacognition questions:
1. Which treatise(s) would you consider to be The Tai Chi Classics? Which author is most accessible to you? And which parts do you struggle to put into your practice?
2. What role does 'shen' play in tai chi?
3. Explain the significance of 'folding'.
4. The name of the Art refers to the 'yin/yang' diagram... So, how does tai chi use yin/yang?
5. Illustrate the difference between 'jing' and 'li'. What bearing does this have on 'peng'?
6. What does the expression 'invest in loss' refer to?
7. Explain the difference between the first 4 powers and the second 4 powers.
8. Which of the Taoist Classics do you find most relevant/pertinent to tai chi? And why?
9. What is 'mutual arising'?
10. How does '4 ounces of pressure' operate in practice? What are the active/passive manifestations? And how do they differ?
If a tai chi teacher cannot answer every question comprehensively - verbally & physically - they are not skilled enough to be an instructor. Look for somebody who can provide good answers.