Should, ought to and had better.

1. I'm very tired. I should go to bed.

2. You should bring the car to the mechanic if you don't want it to break down.

3. - Mariana, you don't look very well, you ought to go to the doctor.

4. I had better go to the bank tomorrow because it's too late.

5. It's raining. You had better take an umbrella.

6. Peter's father is waiting for him. He had better not be late.