My approach, be it a package like Word or a language, is to skim through the documentation. But don't try and remember everything - just note things it can do, but not necessarily how.
Of course there are always basics that have to mastered, such as general language syntax and controls structures like "for" and "while" loops, "if, else" etc.
Then, when you need to do something it's "Ah, I remember seeing something that may help." The reference manual is then there to find what it was it and read how.
The next thing it throw myself into the deep end and use it, as Chrysanthus suggests.
hth
