Your question is a very difficult one. Here's one guy's take on it
http://www.norvig.com/21-days.html . In general you have to find a problem you want to solve, pick a language, learn the language while solving then problem, and then go back to step one. It's hard to give better advice, (like what language to learn and so on) unless you tell us a bit more about yourself and what you want to do.