I mean what is your way of doing thing when you need to get productive very fast but you don't know anything about THE language? Especially when there is no book available?
Should be community wiki.
Trial and error! No faster way to learn than to make mistakes, IMHO.
Find someone who shares the passion with you and study/learn together.
Samples. Find sample code by doing searches. Get the sample code working, then modify it to suit your needs. As you tackle each part of the code to make your own changes, find relevant documentation and study it until you feel comfortable with the principles, constructs, methods, etc.
Find some demo programs an study them. After you know at least the basic structure of the new language and can compile/run programs with it try creating small projects of increasing complexity that you know how to write using other languages. For instance: a program that read a text file and do some processing and write a new file. It will be more helpful if you create a program that is useful in your daily tasks so you can improve it routinely. Example: add an interface (menu, dialogs, etc). Doing that will help you to explore the function library of the new language.
This is my method...
Start with a very small example.
Build on it step by step.
Make sure you understand each step.
After a while, if your example becomes too complicated.
start with a new simple example.
Take a break every so often for a few minutes.
Also, search on SO for questions in that language and read the answers.
What language are you trying to learn?
When starting from scratch, learn how to do the basic things:
- File I/O
- user input, graphical and non-graphical
- output, graphical and non-graphical
- string manipulation
- error handling
- standard app structure in your language
This isn't a comprehensive list, but it should help get you started, and the Internet is your best friend.