Infinitive or -ing form?

Infinitives and -ing forms are often used in similar ways. For instance, they can follow certain verbs, adjectives or nouns (Infinitives, -ing forms and past participles after nouns, verbs, etc). Compare:

• He agreed to wait.
  He suggested waiting. (not He suggested to wait.)
• She’s ready to listen.
  She’s good at listening. (not She’s good to listen.)
• the need to talk
  the idea of talking (not the idea to talk)

Unfortunately, there is no easy way to decide which verbs, adjectives and nouns are followed by -ing forms, and which are followed by infinitives. It is best to check in a good dictionary.

Expressions with -ing forms can be used both as subjects in sentences, or as complements after be. Infinitives are less common, especially in informal English. Compare:

• Smoking cigarettes can kill you. (More natural than To smoke cigarettes can kill you.)
• My favourite activity is reading thrillers. (More natural than My favourite activity is to read thrillers.)

A bad rule

Students’ grammars sometimes say that infinitives are used when the reference is forward in time, and -ing forms in other cases (as in I expected to see Megan; I enjoyed meeting her parents). Unfortunately, this is not a reliable rule: it’s true when it’s true, but there are too many exceptions. (Compare I anticipated seeing her brother; I was sorry not to meet him.)