A) of verbs after which we use an infinitive with the particle to seem, b) of question words after which we use an infinitive with the particle to how, c) of verbs after which an infinitive is used without a particle to make, d) Infinitive of purpose

1. seem, want, hope, intend, learn, decide, mean, offer, pretend.
2. how to, where to, what to, when to
3. make, help, let; can, must, should, might