Rule 1. A preposition generally, but not always, goes before its noun or pronoun.
He is suffering from fever.
The book is on the table.
Rule 2. The preposition of should never be used in place of the helping verb have.
Correct: she should have done it.
Incorrect: She should of done it.
Rule 3. Follow different with the preposition from. Things differ from other things; avoid different than.
Incorrect: Your brother is different than you are.
Correct: Your brother different from you.
Rule 4. Use into rather than in to express motion toward something. Use in to tell the location.
Correct: They swam in the river.
Correct: The queen walked into the palace.
Correct: The director looked into the matter.
Incorrect: They dived in the water.
Correct: They dived into the water.
Incorrect: Throw these waste papers in the trash.
Correct: Throw these waste papers into the trash.
Rule 5. Prepositions must be followed by nouns, and prepositions can only go on the end of the sentence in certain situations.
Example: She turned the TV on.
If you remove the "on" from the end of this sentence, it would change the meaning. Instead of switching on the set, you would be saying that She turned the TV itself.