i am having dont have idea how and where to use the word a in the sentence. pls help.. i dont have basic knowledge in grammar. pls explain in an easy way. if u have any grammar tricks pls also mention it.

i am also facing trouble in using is, were, has been, etc
can anyone teach me in an easy way. am having exam pls help me

The first part: about "a". Look at any noun. If it's singular (like man), then use "a" or "the". If it's plural (like men), use "some" or "the". The difference between "a" and "the" is that if you are not talking about one particular man, you should use "a". If you are talking about a particular man, you say "the". Also, remember that the plural (for men) is "some" and "the" respectively.

The second part, I think, is about the tenses for "be". In this case, an easy way is to take the three cases (past, present, and future) and the three possibilities (simple, continuous, and perfect). I'll explain.

"Simple" is simple :-) It's used when you don't want to add any extra information.

"Perfect" means that the event is COMPLETE.

"Continous" means that the event is NOT COMPLETE, that it is happening.

So, therefore, you have nine cases. (3 multiplied by 3)

Simple present: "The boy is good."
Simple past: "The boy was good."
Simple future: "The boy will be good."

Now look at the perfect. This means the event is complete, so in the past, the boy was good, PLUS it is finished. That becomes
"The boy HAD BEEN good." (Past perfect)

In the present, the boy is good, PLUS it is finished. So it is "The boy HAS BEEN good." (Present perfect)

In the future, the boy will be good, so say you are talking about tomorrow. For the perfect, you cannot say whether he will still be good day after tomorrow. In that case, it becomes
The boy will have been good (Future perfect).
What this means is, that tomorrow, the boy will be good, but YOU DO NOT KNOW about day after tomorrow.

Finally, look at CONTINUOUS. This is something that is not finished; it is happening.

So, past continous: The boy WAS BEING good.

Present continuous: The boy IS BEING good.

Future continuous: (there's no future continuous for "be", so here it is for "eat"): The boy WILL BE EATING.

The word "a" is used to refer to one person, place or thing and is used normally before the noun(name of person/place or thing).

As to an easy way to learn grammar, let me be honest and say, there is no easy way, atleast as far as English grammar is concerned.

There are a large number of grammar text books. There is an online e-book which you can purchase and the link is grammarmadeeasy.com

All the best in your studies.