Verb is added with -s/-es if the subject is 3rd person singular personal pronoun.
e.g. A bird sings outside my windows.
It sings loudly
Ann sings beautifully
She sings songs to her children
Tom sings very well
He sings in a chorus

(Examples are taken from Fundamentals of English Grammar)

There are three types of Tenses in English:

* Simple Tenses
* Progressive Tenses
* And Perfect Tenses

Each type has a structure for conjugation and is given an auxiliary to perform it. Since there are only three auxiliaries and to be fair we give an auxiliary to each category. Therefore, Do is used with simple tenses, Be with progressives, and Have with Perfect Tenses.
The time is divided into three parts: The Past, the Present, and the Future, so each type of tenses has three parts.

SOURCE :

http://www.english.errachidia.org/ideaabout_tenses.htm

tenses chart

Pattern :

Affirmative Verbal : S + verb 1 + O
e.g. I like English (Remember:A sentence using third person pronoun, the verb should be added with s/es. e.g. She likes English, He brings the bag, It breaks the glass.

Affirmative Non verbal : S + to be present (is, am, are) + Non verbs (adjective/noun/adverb)
e.g. I am happy, they are students, He is here

Negative Verbal : S + Do/Does + not + v1 + O
*note : We use do for Subjects: I, You, They, We
and does for : He, She, It (3rd person pronoun)
e.g. I don't like it, They don't do that, He doesn't bring the umbrella, etc.

Negative Non Verbal : S + To be Present + not + Non verbs
e.g. I am not happy, they are not students, He is not here

Interrogative Verbal
Yes/No Question
Do/Does + S + Verb 1 + O e.g. Do you like the show? Does She like it?
Wh Question + How / Information Question
Who, what, when, where, why and how + Do/Does + S + Verb 1
e.g. What do you do? When does she go to the barber shop? Why do you love me? etc.
It is a bit different if we use who for asking subject. We don't need do or does.
e.g. Who wants to be a millionaire? I do. Comparing to who for asking object Who(m)do you ask? I ask my father.

Interrogative Non Verbal :
Yes/No Question
To be Present + S + Non Verb e.g. Are you happy?
Wh Question + how / Information Question
Who, what, when, where, why and how + to be present + S + Complement
e.g. Who are you? what is that? How are you?