Yes. (answer to yes/no question)
HIja' or HISlaH
No. (answer to yes/no question)
Yes, OK, I'll do it.
lu' or luq
No, don't, I won't.
Hello. (Roughly, "What do you want?")
I don't understand.
Good! (expression of satisfaction)
Where is the bathroom?
nuqDaq 'oH puchpa''e'
yI'el (to more than one person: pe'el)
naDevvo' yIghoS (to more than one person: naDevvo' peghoS)
Open the door!
lojmIt yIpoSmoH! (See note if you think something is missing here.)
Don't be silly.
yIDoghQo' (to more than one person: peDoghQo')
Your mother has a smooth forehead!
Hab SoSlI' Quch! (Note: this is a powerful insult; don't say it to friends.)
Today is a good day to die.
Heghlu'meH QaQ jajvam
We are Klingons!
qoSlIj DatIvjaj (to more than one person: qoSraj botIvjaj)
What time is it?
'arlogh Qoylu'pu'? (Literally, "How many times has it [presumably some traditional hour alarm] been heard?")
bIjatlh 'e' yImev (to more than one person: Sujatlh 'e' yImev)
That's great news!
buy' ngop (Literally, "The plates are full")