Subject verb agreement is an aspect of English grammar that Chinese students often forget about because there is no equivalent modification of verbs to make them agree with their subjects in Chinese.

Regular verbs add -s or -es (after ss, x, sh or tch) in the third person singular (He, she or it)

Very few verbs have irregular present forms.

They are:

'to be': I am, you are, he/ she/ it is

'to have': I have, you have, he/she/it has

'to do': I do, you do, he/she/it does

'to go': I go, you go, he she/it goes

Only one verb marks subject verb agreement in the past tense:

'to be': I was, you were, he/ she/ it was

Uncountable words are treated as singular, as are the following: somebody, everybody, nobody, someone, none, nothing etc.

Remember that when subjects are connected with 'or', the subject that is closer to the verb will determine the number of the verb (whether it is singular or plural).

A very clear and detailed account of subject-verb agreement is given at: http://www.write.armstrong.edu/handouts/SVcontextexercises.pdf

The following exercises may also help.
Exercise

http://aliscot.com/bigdog/agrpa_exercise.htm

http://elc.polyu.edu.hk/ErrorCorrection/agreement1.htm