Basic sentences follow the pattern: Subject — Verb — Object.
Here is an example:
To identify the subject, look for the noun that is doing the action indicated by the verb. The object is the noun receiving the action. The first noun in the sentence, dog, is performing the action indicated by the active verb, ate. The noun dog is therefore the subject of the sentence. The only remaining noun, homework, is the object. This noun describes what the dog ate.
Some sentences stray from this pattern. In sentences that begin with the adverbs Here or There, the subject follows the verb. When all nouns in the sentence follow the verb, it can be very difficult to figure out which of those nouns is the subject. What should you do in those situations?
Let’s look at an example:
Incorrect: There is many reasons why I can’t help you.
This sentence contains two verb constructions (is and can’t help) plus three nouns/pronouns (reasons, I, and you). The subject is the noun that comes directly after the first verb: There + is/are + subject. The rest of the sentence is a subordinate clause. Since the subject, many reasons, is plural, it takes the plural verb are.
Correct: There are many reasons why I can’t help you.
The subordinate clause why I can’t help you has no effect on subject-verb agreement in the main clause. This part of the sentence functions as a direct object.
Note that there is only one noun reasons and one verb are in the main clause. Ignore nouns and verbs in dependent clauses and “filler” phrases when hunting for the subject and main verb.