Usage of prepositions

A preposition is a word or set of words that indicates location (in, near, beside, on top of) or some other relationship between a noun or pronoun and other parts of the sentence (about, after, besides, instead of, in accordance with). A preposition isn’t a preposition unless it goes with a related noun or pronoun, called the object of the preposition. 
Now When You Have Understood What Is The Meaning Of Term Prepositions. Let's Start With RULES For Better Understanding And Scoring High Marks In Your Competitive Exam English  Section. 

Preposition Rules And Examples 

1. Objective case (of Noun or Pronoun) is used after Preposition. 

For Example

Incorrect– I do not depend on he. 

Correct– I do not depend on him.   

2. The Prepositions used after two words must be made clear if these two words are connected by and or. 

For example 

Incorrect– She is conscious and engaged in her work. 

Correct– She is conscious of and engaged in her work.

3. If a Principal Verb is used after about, after, at, before. for, from, in, on. to, that Verb must be in ing (V4) form. 

For example 

Incorrect– You prevented me from do it. 

Correct– You prevented me from doing it. 

4. On, in, at are not used before today, tomorrow, yesterday, the following day, the next day etc. 

For example 

Incorrect– He will go there on tomorrow. 

Correct– He will go there tomorrow. 

5. No Preposition is used before the word home. At home is a phrase which bears a different meaning. 

For example

Incorrect– Bring a T.V. set at home. 

Correct– Bring a T.V. set home. 

6. After Transitive Verbs, like discuss, describe, reach, order, tell, demand, attack, resemble, ridicule, etc. we directly use the object and no Preposition is used after the Verb. 

For example 

Incorrect– The poet describes about the beauty of natural in this poem. 

Correct- The poet describes the beauty of nature in this poem. 

7. Say/suggest/propose/speak/reply/explain/talk/listen/write is followed by to- Preposition if there is a person in the form of object. For example

 A. Incorrect– He did not reply me. 

Correct– He did not reply to me. 

B. Incorrect– He did not write to a letter. 

Correct– He did not write a letter.

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