Different verbs are followed by different forms: some take INFINITIVE (to + verb), some take GERUND (verb + -ing), some take BOTH. There's no rule - you must MEMORIZE the patterns!
Practice tip: Make verb lists! Infinitive list: want, decide, plan, hope, promise. Gerund list: enjoy, finish, keep, mind, avoid. Both: like, love, hate, start. Review regularly!