Find the helping verb in the sentence.
If the helping verb is in negative form the question tag would be in positive form.
*He didn't eat,did he?
If the helping verb is in positive form the question tag would be in negative form.
*He did his homework,didn't he?
Never,seldom,rarely - tag in positive (does or do)
Now when no auxiliary verb is given the rules to follow are:
Verb in Sentence question tag
(i,you,we,they) goes do
(he,she,it) goes does
(he,she) is is
(you) are are
(i ) am am or ain't i
Let us shall
singular -present tense-does