Is it correct to put a comma before an adverb?

No, you do not use a comma before words like tonight, now, or soon when they come at the end of a sentence. Generally, adverbs are only set off by commas when they are at the beginning of the sentence or when they appear before the verb phrase of the main clause. Adverbs are more than just single words though. You can have adverb phrases and adverb clauses that function in the same manner as a single word adverb. Adverbs modify more than just verbs. They also modify other adverbs and adjectives.