'to look on' means to watch something happen.
- The Police just looked on as the demonstrators marched peacefully through the streets.
- Nobody helped me. They just looked on as I struggled to get up off the street.
'to look on' also means to consider someone or something in a special way.
- We are very close. I look on him as my brother.
- Don't look on not getting the job as a failure. It's not.
'to look out' means be careful. It is always an order.
- Look out! The boss is coming.
- Look out! You're going to fall.
'to look out for' means to watch carefully around you so you will notice something or someone in particular.
- When you go to the conference, look out for Anna. She will be there.
- Janet is twenty next week. Can you look out for a present when you are in the shops?
'to look out for' can also mean to take care of someone.
- Will is a great brother. He always looks out for his sisters.
- She's very selfish. She just looks out for herself.
'to look over' means to quickly examine something.
- At the end of the exam, I only had a few minutes to look over what I had written.
- The doctor quickly looked him over before sending him for an x-ray.
'to look round' means to walk through a building or place to have a look at it.
- When you travel on business, you don't have time to look round the places you visit.
- The first time we looked round the house, we knew it was the house for us.
'to look through' means to quickly examine a text or some things.
- I decided to give half my clothes away when I had looked through them.
- We looked through the list of applicants and made a shortlist of the six best qualified.
'to look up' means to find a piece of information in a book or other source of information.
- I didn't know the word so I looked it up in the dictionary.
- I looked their address up in the Yellow Pages.
'to look up to' means to respect and admire someone.
- My father's wonderful. He's the person I most look up to.
- All his employees look up to him and admire him.