When one verb follows another they can follow one of several patterns, for example:
- verb + to-infinitive
- verb + -ing form (gerund)
- verb + to--infinitive / -ing form
- verb + object + (to-) infinitive
- verb + object + -ing form
- verb + that clause
There are unfortunately no hard and fast rules as to what pattern to use, although a to-infinitive often looks forward and/or involves an action - He decided to do it (he decided, then he did it), while an -ing form often looks back or is more about reactions, thought processes or emotions - She enjoys kite surfing (she enjoys the experience).
There's a link at the top of this page to a reference page with lists of verbs and their possible patterns, but the only real way to learn these patterns is through practice and exposure: ideally, 'afford to do' and 'admit doing', etc, should come as automatically to learners as 'sing, sang, sung'.
The exercises in this post (especially the first one), will hopefully help you practise these patterns, so that they become automatic. There are also a couple of quizzes to practise using dependent prepositions after verbs.
