RULE # 1 : RULE # 1 When Main clause is in Present Indefinite Tense then Subordinate Clause will be in Future Indefinite Tense
Ex. I think it’ll rain today.
He knows that he will not come to the class today.
RULE # 2 : RULE # 2 When Main Clause is in Past Perfect Tense then Subordinate Clause will be in Past Indefinite Tense.
Ex. He had gone before I reached home.
The boss had left before they went to his office.
RULE # 3 : RULE # 3 When Main Clause follows Would/Could V1, in this case Subordinate Clause will be followed by Past Indefinite Tense.
Ex. She would tell you if you asked her.
He would disclose the truth if I did not make him understand.
RULE # 4 : RULE # 4 When Main Clause follows Would/ Could Have + V3, in this case Subordinate Clause will be followed by Past Perfect Tense.
Ex. I would have helped him if he had asked for help.
They would have breached the contract if I had not convinced them.
RULE # 5 : RULE # 5 When Main Clause follows Past Indefinite Tense and there is Universal Truth in Subordinate Clause, in this case the Subordinate Clause will always follow Present Indefinite Tense.
Ex. I told him that ‘The sun rises in the East’.
He said that ‘Live and Let live’ is a good principle.
RULE # 6 : RULE # 6 When Main Clause follows Past Indefinite Tense in that case the Subordinate Clause will also follow Past Indefinite Tense.
Ex. He told me that he went to see cinema.
She inquired if he stole her pen.