1. INFINITIVE OR ING-FORM

2. The to-infinitive is used:
To express purpose (in order to)
Example: Carl called to talk about our plans for tomorrow.
After certain verbs (agree, appear, decide, expect, hope, plan,
promise, refuse, bother, demand, fail, manage, offer, seem, be supposed, threaten, choose, intend, advise, allow, enable, encourage, forbid, force, invite, order, permit, persuade, recommend, remind, teach, tell, warn etc)
Example: They decided to move to Italy.
After would like, would prefer, would love etc, to express a specific preference.
Example: I would like to study English.

3. After adjectives which describe:
feelings/emotions (happy, sad, glad)
Example: I am happy to be here.
willingness/unwillingness (willing, eager, reluctant)
Example: She is always willing to help.
After too/enough
Example: It isn’t warm enough to go out without a jacket.
To talk about an unexpected event usually with only.
Example: I arrived at the airport only to find that my flight had been cancelled.
With it + be + adjective/noun.
Example: It was easy to find the house after all.

4. After be + first/second/next/last.
Example: She was the first to come.
After verbs and expressions such as ask, learn, explain, decide, find out, want, want to know when they are followed by a question word.
Example: The maths teacher explained how to solve the problem.
Note: Why is followed by subject + verb, not an infinitive!
Example: I wonder why she didn’t come.
In the expressions to tell you the truth, to be honest, to sum up, to begin with.
Example: To tell you the truth I didn’t expect that you would come.
Note: if the to-infinitives are linked by and or or the to of the second infinitive can be omitted.
Example: I would like to go and see what is happening.

5. The infinitive without to is used:
After modal verbs.
Example: She can speak English.
After the verbs let, make, see, hear and feel.
Example: They made him come.
Note: See, hear, listen to, notice, feel and watch can be followed by an ing-form with a change in meaning, to describe an incomplete action.
Example: I saw her fall = I saw her while she was lying on the floor.
I saw her falling = I saw her while she was falling.

6. After had better and would rather.
Example: We had better take the train because the traffic is very bad at the moment.
Note: Help can be followed by either the to-infinitive or the infinitive without to.
Example: She helped me (to) choose the carpet for the living room.
The negative is formed by placing not before the infinitive
Example: We decided not to participate in the race.

7. The ing-form is used: as a noun (subject or object)
Example: Smoking is very bad for your health.
Not going to Italy is the worst decision I have ever made.
After certain verbs: admit, appreciate, avoid, continue, deny, fancy, go (for activities), imagine, mind, miss, quit, save, suggest, practise, consider, prevent, involve, finish, keep...
Example: Can you imagine winning the race?
After love, like, enjoy, prefer, dislike, hate, to express general preference, but for a specific preference we use would like, would prefer, would love with to-infinitive.
Example: I like dancing. I would love to dance.

8. After expressions such as be busy, it’s no use, it’s (no) good, it’s (not) worth, what’s the use of, can’t help, there’s no point in, can’t stand, have difficulty (in), have trouble.
Example: There’s no point in talking to you about it, you never listen.
After spend, waste or lose (time/money).
Example: He spent a lot of time listening to music.
After the preposition to with verbs and expressions such as look forward to, be used to, in addition to, object to, prefer (doing sth to sth else).
Example: He prefers playing tennis to swimming.
After other prepositions.
Example: He was thinking of going to the seaside by car.

9. Difference in meaning between to-infinitive and ing-form
Some verbs can take either the to-infinitive or the ing-form with a change in meaning.
Forget + to-infinitive = not remember (He forgot to lock the door)
Forget + ing-form = not recall ( I’ll never forget travelling to Italy)
Remember + to-infinitive = not forget (Don’t remember to turn off the lights)
Remember + ing-form = recall (I remember talking to Jane at the party)

10. Mean + to-infinitive = intend to (I never meant to hurt you)
Mean + ing-form = involve (If I get the job it will mean moving to the centre of the town)
Regret + to-infinitive = be sorry to (We regret to inform you that the meeting has been cancelled)
Regret + ing-form = feel sorry about (I regret losing touch with my old friend Tom)
Try + to-infinitive = do one’s best, attempt (I tried to call you, but I couldn’t get through)
Try + ing-form = do sth as an experiment (Why don’t you try changing places with her?)

11. Stop + to-infinitive = stop temporarily in order to do sth else
(After a couple of hours we stopped to have a rest)
Stop + ing-form = finish doing sth
(I stopped smoking because it’s not good for my health)