1) STRUCTURES WE CAN USE IN THE MAIN CLAUSE:
a) Would have done / would have been doing
Perihan didn't wear a coat, so she caught a cold.
If she had worn a coat, we wouldn't have caught a cold.
Senem started to work late, so she was still working at midnight.
If Senem had started to work earlier, she wouldn't have still been working at midnight.
b)Would have had to and Would have been able to
If someone had helped me ,I wouldn't have had to work still midnight.
If I hadn't run, I wouldn't have been able to catch the bus.
c) Modals ( might , could ... )
He had the necessary qualifications, so he got the job.
If he hadn't had the necessary qualifications, he might not have got the job.(=Perhaps he wouldn't have got the job.)
I learned all the prepositions by heart, so I did well on the test.
If I hadn't learned all the prepositions by heart, I couldn't have done well on the test.
Henry might have lent his car if we had asked him.
You could have caught your train if you had left ten minutes earlier.
2)STRUCTURES WE CAN USE IN THE-IF CLAUSE
a)Past Perfect Tense
He didn't obey the speed limit, so he got a ticket for speeding.
If he had obeyed the speed limit he wouldn't have got a ticket for speeding.
If I had seen Atatürk, I would have been the happiest man in the world.
If they had invited us , naturally , we would have gone to the party.
He would have been very angry if he had learned the truth.
You wouldn't have caught cold if you had worn your overcoat.
b)Past Perfect Continuous
He wasn't wearing his seat-belt at the time of the accident ,so he got badly injured.
If he had been wearing his seat-belt at the time of the accident, he wouldn't have gotten injured so badly.
If Betül hadn't been sleeping when the exam started, she could have passed the test.
I would not have come up the stairs if the lift had been working .
c)Had had to and been able to:
I had to work on my project last night, so I missed my favourite programme on tv.
If I hadn't had to work on my project last night, I could have watched my favourite programme on tv.
They were able to persuade their landlady, so she paid for the burst pipe in the bathroom.
If they had been able to persuade their landlady, she wouldn't have paid for the burst pipe in the bathroom.
d)If it hadn't been for=But for
This expression is used to explain why something didn't happen in the past.
If it hadn't been for your help, I would have failed the exam.
But for your help ,I would have failed the exam.