Allow me to introduce the most common question words and some examples on how to use them.

Who = shei2 or shui2 (shei2 I believe is more common and is what I personally use)

In English “who” is normally the first word in a question whereas in Chinese it can appear at the end or beginning depending on the question.  Here are some examples :

Who are you ? = ni3 shi4 shei2 ? (literally = you are who ?)

Who would like to eat lunch ? = shei2 xiang3 chi1 wu3fan4 ? (literally = who would like eat lunch – here the grammar and word order is identical to English)

Who is the best ? = shei2 shi4 zui4hao3de ? OR zui4hao3de shi4 shei2 ? (literally = who is best ? OR best is who ?)

What = shen2me

In English “what” is normally the very first word in a question, however in Mandarin it is commonly the last word.

For example the question :

What are you doing tomorrow ?

In Chinese is :

Ni3 ming2tian1 hui4 zuo4 shen2me ? (literally = you tomorrow will do what?”)

Some more examples :

What is this ? = zhe4 shi4 shen2me ? (literally = this is what?)

What would you like to eat ? = ni3 xiang3 chi1  shen2me ? (literally = you would like eat what ?)

What is your problem ? = ni3de wen4ti2 shi4 shen2me ? (literally = your problem is what ?)