1) An infinitive verb almost always begins with to followed by the simple form of the verb.
Dick likes to run often.
Dick wants to fly planes.
Dick used to walk to work.
2) An infinitive is not doing the work of the verb of the sentence. Don't add s, es, ed, or ing to the end.
Adjective: The only way Dick would survive his boring job was to dream about his gig at the bar.
Adverb: Dick, an aspiring songwriter, suffered through his job at the tax office to pay for necessitities until his big break arrived.
Incorrect: Sally wanted to thoroughly kiss him.
Correct: Sally wanted to kiss him thoroughly.
For effect: Sally wanted to kiss him, thoroughly.
This rule is broken frequently. If you choose to split infinitives, do it intentionally and for emphasis, not because you don't understand the rule.
You can search and kill for the word to.
You could also search and kill for word pairs: wanted to, tried to, ought to, used to, liked to, etc.