Rule 1: A pronoun is used in objective case after Let/ Between/ Preposition/ Any.
Example:
Let her complete the homework.
You have to choose between Geeta and me.

Rule 2: A pronoun should be used in same form while comparing with than.
Example:
 I know her better than him. 

Rule 3: Order of personal pronoun should be 231 (i.e. Second person, Third person, First person)
Example:
You, she and I are going to play Cricket. 
Rule 4: A reflexive pronoun or an objective pronoun must be put after the verbs hurt, cheat, acquit, absent, avail, prostrate, introduce, present, enjoy, resign, revenge, apply, exert, adopt, adjust etc.
Example:
You should give yourself some rest.

Rule 5: A reflexive pronoun can not be used in place of subject.
Example:
Deepak and I decided to play cricket. 

Rule 6: Since a personal pronoun is used instead of a noun, it must be of the same number, gender and person as the noun for which it stands.
Example: 
Those beggars are idle. They refuse to work for their living. (Here the pronoun they is of the same number and person as the noun beggars.)

Rule 7: When a pronoun stands for a collective noun, it must be in the singular number if the collective noun is thought of a whole.
Example: 
The fleet has reached its destination.
The jury will give its verdict in a few hours.

Rule 8: If the reference is to the individual members of the group, a pronoun standing for a collective noun must be plural in number.
Example:
The jury are still debating the issue and will announce their individual opinions in a few hours.

Rule 9: When two singular nouns joined by and are preceded by each or every, the pronoun must be singular in number.
Example:
Every man and every boy should be ready to defend his country.

Rule 10: When two singular nouns are joined by or, either…or or neither…nor, the pronoun should be singular in number.
Example:
Neither Peter nor John has brought his book. (NOT Neither Peter nor John have brought their books.)