The main verb in a sentence is the verb in the main clause, also called the independent clause. This verb will appear in conjugated form, showing tense, person, number, and mood. Other conjugated verbs might appear in a sentence, but these will be verbs in dependent clauses.
It's also possible to have two or more main verbs hanging on the same grammatical subject. If you have two main verbs, do not use a comma before the conjunction. Thus:
John hit the ball and ran to first base.
John hit the ball, ran to first base, and slid into second.