We use the gerund after...1. ... certain verbs, such as: continue, enjoy, finish, like, love, prefer, remember, start.
2. ... after prepositions, such as: at, in, with, etc.
3. after some expressions, such as: look forward to...
We use the to infinitive after...
1. certain verbs, such as: agree, ask, decide, forget, help, hope, try, want.