Learn Hardcore Spanish (Latin America): Ni siquiera mis amigos saben lo que diré en la presentación. - Not even my friends know what I will say in the presentation.

It means not even and adds strong emphasis or surprise, highlighting an extreme case. In the sentence, it underscores that if even your friends (the people most likely to know) don’t know, then nobody does.

Do I need to add no with ni siquiera?

If the negative word comes before the verb, you do not add no: Ni siquiera mis amigos saben…
If it comes after the verb, you do add no: Mis amigos no saben ni siquiera… This follows Spanish negative-concord rules.

Can I move ni siquiera around in the sentence?

Yes, with small differences in emphasis:

Ni siquiera mis amigos saben lo que diré… (strong focus on friends)
Mis amigos ni siquiera saben lo que diré… (focus on the degree of their ignorance)
Mis amigos no saben ni siquiera lo que diré… (same meaning; requires no because ni siquiera follows the verb)

Can I drop siquiera and just say Ni mis amigos…?

Yes. Ni mis amigos saben… is valid and means not even my friends. In Latin America, ni siquiera is more common and a bit clearer/emphatic.

Why is it saben (from saber) and not conocen (from conocer)?

Use saber for knowing facts/information and conocer for being acquainted with people or places.

saber: saben lo que diré = they know the content
conocer: conocen a mis amigos = they are acquainted with my friends

What does lo que mean here?

It’s the neuter lo plus the relative pronoun que, meaning what/that which. saben lo que diré = they know what I will say. It turns the whole clause diré en la presentación into a noun-like object of saber.

Could I use qué instead of lo que?

Often, yes: saben qué diré en la presentación is acceptable and common. Both versions mean they know what I’ll say. Subtly:

lo que = that which (slightly more neutral/statement-like)
qué = an indirect question (feels a bit more question-like) Do not confuse que (no accent, that/which) with qué (accented, what).

Why is qué not accented in lo que?

Because it’s the relative pronoun que, not an interrogative. Only the interrogative/exclamative form carries an accent: qué. So: lo que (no accent), but qué diré (accent).

Why is the verb mix present (saben) + future (diré)?

Spanish often expresses current knowledge about a future event with present + future: they currently don’t know the content of a future statement. It’s natural and idiomatic.

Could I say voy a decir instead of diré?

Yes: lo que voy a decir is very common in Latin America for near or planned future. diré is also correct; it can sound a bit more formal, succinct, or definite. Meaning here is the same.

Why is it en la presentación and not a la presentación?

en la presentación = in/at the presentation (location/time frame)
a la presentación = to the presentation (direction/goal) Here you mean at/in, so en is right. You could also say durante la presentación for during.

Can I replace lo que diré with lo to avoid repetition?

If the context already makes the content clear, yes: Ni siquiera mis amigos lo saben. But in your original sentence, lo que diré en la presentación introduces the content for the first time, so you need the full clause.

Is presentación the best word? Are there synonyms?

Presentación is a safe, common choice. Alternatives:

charla (talk, informal)
ponencia (conference paper/talk, academic)
discurso (speech, more formal/ceremonial) Pick based on context/register.

Any pronunciation or accent-mark tips for this sentence?

ni si-QUIE-ra (stress on -quie-), no accent on siquiera.
sa-BEN (saben), plain b.
di-RÉ (diré), written accent on -ré.
pre-sen-ta-CIÓN (presentación), written accent on -ción.
lo que: que has no accent here. Keep the r in presentación soft; the d in diré is a clean d sound.

Is tampoco a synonym of ni siquiera?

No. tampoco = not either/neither (adds another negative item). ni siquiera = not even (intensifies the degree). Example:

No lo saben mis amigos tampoco. = My friends don’t know it either.
Ni siquiera mis amigos lo saben. = Not even my friends know it (stronger).