Learn Hardcore Norwegian: Jeg legger helsekortet i bokhyllen slik at jeg husker hvor det er neste gang. - I put the health card on the bookshelf so that I remember where it is next time.

Because å legge means “to lay/put (something somewhere)” and takes a direct object, while å ligge means “to lie/be located” and describes the state of something.

You use legger when you actively place the card: Jeg legger helsekortet …
You use ligger to describe where it ends up: Helsekortet ligger i bokhyllen. Forms to know:
å legge – legger – la – har lagt
å ligge – ligger – lå – har ligget

Is i bokhyllen correct, or should it be på bokhyllen / på hylla?

I bokhyllen is natural when you mean “on a shelf/in the bookcase (among the books).”

i (bok)hyllen/hylla = inside the shelving unit, on one of its shelves.
på bokhyllen typically means “on top of the bookcase.” Note: Many speakers also say på hylla for “on the shelf,” but i hylla is very common and often preferred when you mean “on a shelf within the unit,” not on its top surface. Dialect and personal preference vary.

What does the -et in helsekortet tell me?

It’s the neuter definite ending. Helsekort is neuter:

indefinite singular: et helsekort
definite singular: helsekortet
indefinite plural: helsekort
definite plural: helsekortene

Why bokhyllen with -en and not -et?

Because bokhylle is a common-gender (or optionally feminine) noun, not neuter.

indefinite: en/ei bokhylle
definite (common-gender form): bokhyllen
definite (feminine form, also allowed in Bokmål): bokhylla

Can I say bokhylla instead of bokhyllen?

Yes. In Bokmål you can use feminine forms for many nouns. Bokhylla is common and sounds slightly more informal/conversational than bokhyllen. Both are correct.

Should there be a comma before slik at?

It’s common (and recommended by many style guides) to add a comma: …, slik at … because it introduces a subordinate clause. In short, straightforward sentences you may see it omitted, but the comma is a safe choice.

What’s the difference between slik at and for at?

for at is the “purpose” connector (“in order that”), especially in more careful/written language. It often pairs with skal/kan: … for at jeg skal huske …
slik at typically expresses result/consequence (“so that”), but in everyday speech many people also use it for purpose: … slik at jeg husker … In your sentence, both are acceptable. “Schoolbook” style would favor for at (jeg skal huske) for intentional purpose; casual speech often uses slik at (jeg husker). Colloquially you’ll also hear sånn at.

Could I say for å huske instead?

Yes: Jeg legger helsekortet i bokhyllen for å huske hvor det er neste gang.

for å + infinitive is a compact way to express purpose when both clauses have the same subject (jeg). It’s very idiomatic here.

Why is it hvor det er and not hvor er det?

Because it’s an embedded (indirect) question inside a subordinate clause. Norwegian keeps normal subject–verb order in embedded questions:

direct question: Hvor er det?
embedded: … hvor det er (not hvor er det)

Why not der instead of hvor in hvor det er?

Use hvor in content questions (“where?”) and embedded questions (“… where it is”). Use der in relative clauses after a noun like “the place”: stedet der det er (“the place where it is”). Here, you’re not modifying a noun; you’re stating what you’ll remember, so hvor is correct.

Why det and not den?

Because helsekort is a neuter noun, so the pronoun is det (not den). If the noun were common gender, you’d use den.

Would hvor det ligger be more natural than hvor det er?

Both are fine:

hvor det ligger focuses on the physical resting position (lie/located).
hvor det er is more general (“where it is”). With small flat objects like a card, ligger is very natural, but er is also perfectly idiomatic.

Do I need future marking (skal/kommer til å) in husker?

No. Norwegian often uses the present for future meaning when time is clear from context (here: neste gang). You could say … for at jeg skal huske …, but … slik at jeg husker … is already natural.

Could I say hvor jeg la det instead of hvor det er?

Yes, but it changes the nuance:

hvor det er = where it is (its location when you need it next time).
hvor jeg la det = where I put it (the past action). Both can be used; pick the focus you want.

Is the placement of neste gang okay? Where else could it go?

Ending the clause with neste gang is natural: … hvor det er neste gang. You could also say:

… hvor det ligger neste gang.
With a pronoun: … slik at jeg husker det neste gang. Avoid placing neste gang too early inside the clause; the end position reads most smoothly.

Does Norwegian have a progressive like “I’m putting”? What does Jeg legger mean?

Norwegian doesn’t have a separate progressive form. Jeg legger … can mean “I am putting … (now)” or “I put … (as a habit),” depending on context. Add adverbs if you need to clarify (e.g., nå for “now,” ofte for “often”).