Arvi Fox

to – infinitive is used

• to express purpose
  he went to a bank to get some money
• after certain verbs (agree, appear, decide, expect, hope, plan, promise, refuse)
  he promised to help us
• after adjectives which
  • describe feelings/emotions (happy, glad, etc.)
  • express willingness (willing, eager, reluctant, anxious, unwilling, etc.)
  • refer to person’s character (mean, clever, etc.)
  • with adjectives lucky and fortunate
    I was annoyed to hear it
    He is reluctant to help
    You were clever not to believe them
    Note: Also impersonal construction possible
    It was clever of you not to believe them
• after certain nouns and pronouns: something, somewhere, anyone, nothing, etc.
  Take something to drink
• after too/enough
  she is too young to stay there
• with it+be+adjective/noun
  it is great to buy a car
• to talk about unexpected events (usually with only)
  They rushed to airport (only) to be informed that flight had been canceled
• after: be + last, first, second, next, best
  he was the first to arrive
• after: ask, learn, find out, wonder, want to know, decide, explain, etc. when they followed by question words (who, what, where, how)
  he explained how to operate the machine
  I don’t know why he left

bare infinitive is used

• after modal verbs
  he should apologise
  but: ought + to infinitive
• after: let, make, see, hear, feel (complete action)
  they saw her talk to the manager.
  but: be made, be heard, be seen + to-infinitive
  she was seen to talk to the manager.
  but: I saw her getting into a taxi. She was seen getting into a taxi.
  but: can/could + see/hear + ing
  we could see smoke coming out of the building
• after had better and would rather
  you had better see a doctor.
• help is followed by either to-infinitive or bare
  she helped me (to) fill in a form

ing form is used

• as a noun
  cycling is a form of exercise
• after: admit, anticipate, appreciate, avoid, consider, continue, delay, deny, discuss, enjoy, escape, excuse, fancy, finish, forgive, go, imagine, involve, keep (= continue), mention, mind, miss, postpone, practise, prevent, quit, recall, recollect, report, resent, resist, risk, save, stand, suggest, tolerate, understand, etc.
  He avoided answering my question.
  They considered moving abroid.
• after: dislike, enjoy, hate, like, love, prefer to express general preference
  she likes painting
  but: would like / would love / would prefer to express specific preference
  I’d like to paint your portrait
• after: be busy, it’s no use, it’s (no) good, it’s (not) worth, what’s the use of, can’t help, there is no point, can’t stand, have difficulty in, have trouble, have a hard time, etc.
  what’s the use of waiting for an answer
• after: spend, waste, lose (time, money)
  we wasted a lot of time trying to find a parking.
  he lost money investing
• after prepositions
  he was found guilty of lying in court
• after preposition ‘to’: look forward to, be used to, get round to, object to, in addition to, prefer, etc.
  she objects to working on saturday
• after: hear, listen to, notice, see, watch, feel to describe an incomplete action
  I listened to James singing a song (means he listened to part of song, not the whole)
  but: bare infitivite to describe a complete action
  I listened to James sing a song