Infinitive with to in English

To-infinitive is used in the following cases:

Verb + to-infinitive

after verbs e.g. agree, arrange, beg, choose, claim, continue, decide, demand,expect, hope, intend, learn, plan, prefer, pretend, promise, resolve, swear, threaten, wish I decided to buy a new car.
He agreed to help her.
We arranged to visit the house on Monday.
after question words I don't know what to choose.
I didn't know how to get in touch with them.
after verb + object + question-word
e.g. advise, instruct, remind, teach, tell
He told us to run.
My sister taught me to swim.
She told me where to wait.
He warned me to stay away.

Adjective + to-infinitive

after adjectives He was kind to help us.
It was kind of her to help us.
How kind of him to help us!
He is eager to please.
He is easy to please.
She is amusing to be with.
Polyester is easy to iron.
It is good to be here.
after the first, the second, etc. She is always the first to arrive and the last to leave.
Who was the first person to arrive at the party?
after 'too' + adjective
adjective + 'enough'
He is too weak to lift it.
I'm too tired to stay up longer.
He's strong enough to lift it.
It is ripe enough (for me) to eat.

Noun + to-infinitive

after nouns related to verbs The decision to wait was wise.
It's their wish to succeed.
His refusal to help surprised them.
after nouns related to adjectives He's determined / eager / willing to help.
I want to thank you all for your determination to help.
It's fun to be here.
after nouns, 'something', 'a lot', etc. There was nothing to do so we watched TV.
I want something to answer the phone.