せんせいはきびしいです。(sensei wa kibishii desu)
The teach is strict.
Add か to the end of the sentence and you get:
せんせいはきびしいですか。(sensei wa kibishii desu ka)
Is the teacher strict?
That's pretty much all there is to it. Here are a few question words:
なに, なん (nani, nan) = what
どこ (doko) = where
いつ (itsu) = when
どうして (doushite) = why
There are two forms of "what," なに and なん. You use なに when it comes before a particle, and you use なん when it comes before a counter*, or です.
なにがおかしいですか。 (nani ga okashii desu ka)
What is (so) funny?
せんせいはなんさいですか。 (sensei wa nansai desu ka)
How old is (the) teacher?
なっとうはなんですか。 (nattou wa nan desu ka)
What is nattō?
*counters are used for when numbering things. The counter for age is -さい
That's all there really is to なに and なん. Make sure that when you ask a question in Japanese, you pronounce か with a rising tone, otherwise you'll sound monotone.