ask somebody for...

= A man stopped me and asked me for money.

belong to...

= Does this book belong to you? (= Is this book yours?)

happen to...

= I can't find my pen. What happened to it?

listen to...

= Listen to the music. It's great!

look at...

= She's looking at her watch.
= Look at these flowers! They're beautiful.
= Why are you looking at me like that?

look for...

= He lost his key, and now he is looking for it.
= I'm looking for Sarah. Have you seen her?

speak/talk to someone about...

= Did you talk to Paul about the problem?
= (on the phone) Can I speak to Chris, please?

take care of...

= When Pat is at work, a friend of hers takes care of her children.
= Don't lose this book. Take care of it.

thank somebody for...

= Thank you very much for your help.

think about... or think of...

= He never thinks about (or of) other people.
= Mark is thinking of (or about) buying a new car.

wait for...

= Wait for me! I'm almost there.

write and call

write (to) somebody

= I never get letters. Nobody writes to me. (or Nobody writes me.)

call somebody (no preposition)

= I have to call my parents. (no call to)

depend

We say depend on...

= A: Do you like to eat in restaurants?
B: Sometimes. It depends on the restaurant.

We can say it depends what/where/how, etc., with or without on.

= A: Do you want to go out with us?
B: It depends where you're going.