How can you learn names of methods or classes of a framework or an API?

Question

I've been programming C++ for a year now. I've gone through the language features and I've written good programs with it, so I decided to move on to OpenGL. At first it seemed confusing. As I kept going through tutorials it appeared to be easier, but I can't remember the names of classes, methods, arguments, etc.

In fact this doesn't just apply for OpenGL; I often get stuck with other frameworks too. I have a program in my head, I know how it would work, but I cannot remember the names of methods or classes to use.

My question here is, in a nutshell, what techniques can you use to memorize those names? Does writing it over and over help you grasp it?