Complicated question. And I'm a learner as well, so take this with handful of salt.
"Jeg kommer til å dra" ("I am going to leave"). "Dette får meg til å skrike" ("This makes me scream"). "Jeg er redd for å svømme" ("I'm scared of swimming").
"For å" often expresses purpose. Any time you see "(in order) to" in English, that's "for å". "Vi kom for å besøke henne" ("We came to visit her"). Doing one verb in order to achieve a second verb.
You'll often see this after adjectives. "Jeg har mye å gjøre" ("I have much to do"). "Det er vanskelig å si" ("It is difficult to say"). Traditional grammar has different names for this type of infinitive, including prolative infinitive, epexegetic infinitive. The function, at any rate, is expanding on the adjective.
Elisabeth's example is good: "Jeg bruker kniven til å kutte salaten" ("I use the knife for cutting the salad").
There are two parts to unpacking the grammar here.
Firstly, English forms both verbal nouns and present participles by adding "-ing". Norwegian, in contrast, sometimes has "-ing" nouns formed from verbs ("ei mening", "an opinion"). But it also often uses "å" or "det å" to create verbal nouns. So "Climbing the mountain was easy" could be rendered as "Å klatre fjellet var lett".
Secondly, "til" in Norwegian is often used after nouns to express something like "for the purpose of". "Stoler til kjøkkenet" ("chairs for the kitchen"); "blomster til blomsterbedene" ("flowers for the flower-beds"); "Har du plass til beina?" ("Do you have room for your legs?"); "Får jeg invitere deg til middag?" ("May I invite you for dinner?").
And, to join both parts of this explanation together: you can simply use a verbal noun instead of a normal noun. "Jeg har ei uke til å planlegge festen" ("I have a week for planning ("=to plan") the party").