Listen. Listen. Listen.
The key is to pay attention and listen to both verbal and non verbal communication.
Imagine that you are a role play as "coach" and is trying to bring the person the another level up after the speech, and he/she indeed need an honest and constructive evaluation from you (the evaluator).
It is given 2 mins for a speech evaluation and the standard format to follow is:
Two important things to note: The speaker's name and his/her subject title.
Begin your evaluation by mentioning the speaker's name and title.
Comment a little bit on the subject matter but not into the details.
Imporatant thing to note is that you must cover the speech objective and
let he/she know that in your opinion, whether all objectives have been fulfilled,
if not, state why with example(s).