Hmmm, hard work to do...

The best source I've got is (if you can believe this) Delphi documentation and on-line Help.

The same API call are well documented in MSDN but it's kinda confusing, because API functions are grouped by category and exactly this is the problem: you don't know the category (you are new in this, remember?) Maybe somebody from MSDN staff hear me :-)

Anyway, the first place to start is MSDN (it's free, thanks God!). If you find a function there, look at the bottom of page. You will find where it's documented (usually a *.h file - .h files are installed by C++). Then try to locate in .h file function parameters and that's all.

Good luck. You will need it.