You need to tell us which language you want to learn. Otherwise it's like saying "I want to learn sports" -- amateur curling and professional football are very different sports. Windows programmers, Mac/iPhone programmers, server-side programmers, Javascript programmers, enterprise Java programmers, and Linux kernel hackers need to focus on different things.

In the absence of details, all we can recommend is basic mental conditioning for programmers. A standard piece of advice is "SICP". Another is "K&R". Eric Raymond's essay on "How to Become a Hacker" is a little dated and a little opinionated, but worth reading. "Learn emacs" (or, to be fair to vi and Textmate, "learn a decent text editor") is a piece of advice that I'm glad I followed.

You cannot go wrong by learning the basics of databases and web application architecture. The architecture of web apps is more important than the choice of server-side language. If it weren't so dated I'd recommend Philip and Alex's Guide to Web Publishing. For a more up-to-date version of that, you might try the required texts for this MIT course: http://philip.greenspun.com/teaching/one-term-web