(1) 这样用的what相当于“先行词+关系代词”，所以其前不能有先行词：
你喜欢什么就拿什么吧。
正：You can have what you like. / You can have everything (that) you like.
误：You can have everything what you like.
(2) 有时what 可用作限定词，其后修饰一个名词：
I gave him what books I had. 我把我所有的书都给他了。
He gave me what money he had about him. 他把身边带有的钱全给了我。
(3) What 后的名词可以是复数名词或不可数名词，但通常不能是单数可数名词：
误：I gave him what book I had. (from www.hxen.com)
(4) What后接不可数名词时，有时可有little修饰。注意区别：what+不可数名词=所有的都，what little+不可数名词=虽少但全部。如：
I spent what time I had with her. 我所有的时间都是与她一起度过的。
I spent what little time I had with her. 我仅有的一点时间都是与她一起度过的。