Learn Hardcore Norwegian: Vennligst ikke forstyrre; møtet har nettopp begynt. - Please do not disturb; the meeting has just started.

The true imperative is forstyrr: Vennligst ikke forstyrr.
Signs and instructions also commonly use bare infinitive after ikke: Vennligst ikke forstyrre.

They mean the same here. Many perceive forstyrr as a bit more “command-like” and forstyrre as a neutral instruction. Do not insert å: avoid Vennligst ikke å forstyrre in this sense.

Where does ikke go in a negative command (especially with vennligst)?

Typical patterns:

Ikke + verb: Ikke forstyrr!
Verb + ikke: Forstyrr ikke!
With “please”: Vennligst ikke forstyrr(e) is the most common on signs. You can also say Forstyrr vennligst ikke, which sounds a bit formal.

Is vennligst the normal way to say “please”?

It’s polite/formal and frequent on signs, emails, and public notices. In everyday speech, native speakers more often use requests like:

Kan du (værsåsnill) la være å forstyrre?
Vær så snill, ikke forstyrr.
Kunne du la være å forstyrre?

Why is there a semicolon, and what else could I use?

The semicolon links two closely related independent clauses. You could also write:

Period: Vennligst ikke forstyrre. Møtet har nettopp begynt.
Colon (introducing the reason): Vennligst ikke forstyrre: Møtet har nettopp begynt.
Dash (informal/emphatic): Vennligst ikke forstyrre – møtet har nettopp begynt. Avoid a bare comma between the two clauses; that would be a comma splice in Norwegian too. If you add a conjunction, a comma is fine: Vennligst ikke forstyrre, for møtet har nettopp begynt.

Why is it møtet and not møte?

Norwegian marks definiteness with a suffix. Møte is a neuter noun:

Indefinite singular: et møte (a meeting)
Definite singular: møtet (the meeting)
Indefinite plural: møter
Definite plural: møtene Here we’re talking about a specific meeting, so the definite form møtet is required.

Could I say Møtet begynte nettopp instead of Møtet har nettopp begynt?

Yes. Both are natural:

Møtet har nettopp begynt (present perfect) emphasizes a recent event with present relevance: it has just started and is now in progress.
Møtet begynte nettopp (preterite) also means “just started.” The nuance difference is small here; both are idiomatic.

Where does nettopp go in the clause?

In main clauses, Norwegian keeps the finite verb in second position (V2). Sentence adverbs like nettopp usually come after the finite verb:

Møtet har nettopp begynt. If you front something, V2 still holds:
Nå har møtet nettopp begynt. In a yes/no question, it comes after the finite verb:
Har møtet nettopp begynt?

What else does nettopp mean besides “just (now)”?

It also means “exactly/precisely,” often for confirmation or emphasis:

Det var nettopp det jeg mente. (That’s exactly what I meant.)
As a one-word response: Nettopp! (Exactly!)

How do I pronounce the tricky sounds?

ø in møtet: like French “eu” in “peu” or German “ö” in “schön.” Approximate as a rounded version of “eh.”
y in forstyrre: like German “ü” in “über.” Rounded “ee.”
Many speakers merge r + s into a retroflex “sh”-like sound, so forstyrre often sounds like “for-shtyrr-eh.” This varies by dialect.
Stress: VÉNN-ligst, for-STÝR-re, MØ-te(t).

Why is there no subject like “du” in the first clause?

Commands in Norwegian (imperatives and prohibition forms) generally omit the subject. The addressee is understood:

(Du) Ikke forstyrr! Adding du is only for special emphasis and can sound brusque.

Can I use starte instead of begynne?

Yes:

Møtet har nettopp startet. Both verbs are common. Nuances:
starte can be transitive (“to start something”): Vi starter møtet kl. 9.
begynne is very general; you can say Møtet begynner kl. 9. or begynne på noe (“begin on something”).

Does begynne take har or er in the perfect?

Standard Bokmål uses har:

Møtet har begynt. You may see er begynt in some dialects/older styles, but har begynt is the safe, standard choice.

If I made the second clause negative, where would ikke go?

After the finite verb:

Møtet har ikke begynt. The pattern is the same with other sentence adverbs: Møtet har kanskje/allerede/akkurat/ikke begynt.