Infinitive without to (Examples: go, speak)

The infinitive of a verb has two forms: the to-infinitive and the infinitive without to. 

Infinitive without to:

We use the infinitive without to after modal verbs can, could, may, might, will, shall, would, should, must, do, let's and
We also use the infinitive without to after let, make and (optionally) help:

• She can sleep in the guest room tonight.
• Will you need to rent a car during your holiday?
• He lets us use some of his land to grow vegetables.
• You can’t make a cat do anything it doesn’t want to do.
• I just want to help you (to) understand the situation better
• I can speak Arabic
• Could you speak more slowly?
• It will rain tomorrow
• You should be at home
• Does he smoke?
• Don't go
• Let's have a drink

We don’t use the infinitive (with or without to) after prepositions:

I should be thankful for reading my blog .

Not: … I should be thankful for read … or … for to read … my blog.