Learn Hardcore German: Bitte komm pünktlich, andernfalls beginnt die Besprechung ohne dich. - Please come on time, otherwise the meeting starts without you.

kommen → komm!
An optional -e is possible in writing or for rhythm: komme!, but komm! is far more common.
The subject du is normally omitted in the imperative.
Bitte softens the command: Bitte komm pünktlich.

How would I say this to more than one person or formally?

Informal plural (ihr): Kommt pünktlich, andernfalls beginnt die Besprechung ohne euch.
Formal (Sie): Kommen Sie pünktlich, andernfalls beginnt die Besprechung ohne Sie.
With the verb sein as an alternative: Sei pünktlich / Seid pünktlich / Seien Sie pünktlich.

Where can I put bitte?

All of these are natural, with slightly different feel:

At the start (neutral/polite): Bitte komm pünktlich, …
After the verb (very common softener): Komm bitte pünktlich, …
As a parenthetical interjection (more emphatic): Komm, bitte, pünktlich, …
Notice there is no required comma after Bitte in Bitte komm …; commas only if bitte is used parenthetically.

What does andernfalls mean and how formal is it?

Andernfalls means otherwise (if not, then…). It’s a sentence‑linking adverb and sounds fairly formal or written. In everyday speech, people more often use sonst. Ansonsten also exists and is a bit more conversational, though it can mean “apart from that” in other contexts.

Can I replace andernfalls with sonst or ansonsten?

Yes:

Bitte komm pünktlich, sonst beginnt die Besprechung ohne dich. (most common in speech)
Bitte komm pünktlich, ansonsten beginnt die Besprechung ohne dich. Nuance:
sonst is the default, everyday choice for “otherwise.”
andernfalls is more formal.
ansonsten can also mean “in other respects,” but here it works as “otherwise.”

Why is there a comma before andernfalls?

Because you’re separating two independent main clauses. In German, when two main clauses are merely juxtaposed or linked by a sentence adverb (like andernfalls/sonst), you must use a comma (or you could use a semicolon or a period):

Bitte komm pünktlich, andernfalls beginnt …
Bitte komm pünktlich; andernfalls beginnt …
Bitte komm pünktlich. Andernfalls beginnt …

Why does the verb come right after andernfalls?

German main clauses are verb‑second (V2). Andernfalls occupies the first position, so the finite verb (beginnt) must be in second position:

First position: Andernfalls
Second position: beginnt
Rest: die Besprechung ohne dich

Is “Die Besprechung beginnt andernfalls ohne dich” also possible?

Grammatically yes, but it’s stylistically marked. When andernfalls functions as a connector meaning “otherwise,” it is most natural at the start of the clause. In mid‑field, it can be read more as “in other circumstances,” which is less clearly a conditional alternative.

Why ohne dich and not ohne dir?

Because ohne always takes the accusative case. Pronouns after ohne:

ohne mich, dich, ihn, sie, es, uns, euch, sie, Sie

What’s the difference between pünktlich and rechtzeitig?

pünktlich = on time, at the agreed/scheduled time. Example: Arriving at 9:00 for a 9:00 meeting.
rechtzeitig = in time/with enough time. Example: Arriving at 8:55 so you’re set up by 9:00. Both are positive; rechtzeitig can be earlier than the exact time, pünktlich is exactly on time.

What exactly is a Besprechung, and are there other words for “meeting”?

die Besprechung (pl. die Besprechungen) = a meeting/discussion, often work‑related but not necessarily a formal “session.”
Alternatives:
- die Sitzung = a formal/session meeting (board, committee).
- das Meeting = loanword, common in business.
- der Termin = an appointment/slot (not the discussion itself).
- das Treffen = a meetup/meeting (neutral, can be informal).
- die Konferenz = a conference. Choose based on formality and context.

Could I use the future tense (wird … beginnen)?

You could, but it’s not necessary. German present tense often covers future meaning:

Natural: …, andernfalls beginnt die Besprechung …
Possible but more formal/emphatic: …, andernfalls wird die Besprechung … beginnen.

Can I express the same idea with a wenn clause?

Yes:

Wenn du nicht pünktlich kommst, beginnt die Besprechung ohne dich. Grammar note:
In the wenn clause (a subordinate clause), the conjugated verb goes to the end: … du nicht pünktlich kommst.
The following main clause is V2: beginnt die Besprechung …

Is there a difference between Bitte komm … and Komm bitte …?

Both are polite. Subtle nuances:

Bitte komm … sounds like a polite request framed from the start.
Komm bitte … uses bitte as a softening particle after the imperative, very common in speech.
…, bitte. at the end adds polite emphasis. Commas are used if bitte is parenthetical: Komm, bitte, pünktlich.

How do I pronounce tricky parts like pünktlich and Besprechung?

pünktlich: ü is a rounded front vowel (shape lips for “oo” while saying “ee”): [pʏ]; final -ch is the “ich‑sound” [ç], not like English “k.” Roughly: “PYNGKT-likh.”
Besprechung: sp at syllable onset is pronounced “shp” [ʃp]; ch again is [ç]; final -ung ends with a velar nasal [ŋ]. Roughly: “buh-SHPRÉH-hoong.”

Anything to know about capitalization and gender here?

die Besprechung is feminine; capitalize all nouns in German.
dich is lowercase (pronoun).
Formal Sie is always capitalized: ohne Sie = without you (formal). Lowercase sie after ohne would mean “her” or “them,” depending on context.