Examples. Were enough examples provided of the structure in a meaningful context? Are you sure the students understood their meanings?
Terminology. Did you call the structure by its (grammar-book) name? If so, was this helpful? If not, would it have helped if you had? What other grammatical terminology was (would have been) useful?
Explanation. Was the information given about the structure at the right level: reasonably accurate but not too detailed? Did you use comparison with the students’ mother tongue (if known)? Was this/would this have been useful?
Delivery. Were you speaking (and writing) clearly and at an appropriate speed?
Rules. Was an explicit rule given? Why/why not? If so, did you explain it yourself or did you elicit it from the students? Was this the best way to do it?
(from Penny Ur ‘A course in Language Teaching’ CUP)
Guidelines on presenting and explaining a new grammatical structure: In general, a good presentation should include both oral and written forms, and both form and meaning.
It is important to have plenty of examples of the structure in the context and to understand them. Visual materials can also contribute to understanding.
Older or more analytically-minded learners will benefit more from the terminology.
Depends on your own situation.
Your explanation should cover the great majority of instances, but too much detail may only confuse. A simple generalization is more helpful to learners than a detailed grammar book explanation.
These are basic and important points! Ask the observer.
You have to ask yourself which is more effective in your situation. If the learners can perceive and define the rule themselves, then let then do it. But don’t waste a lot of valuable class time, sometimes it is better to provide the information yourself
