The hacker attitude is vital, but skills are even more vital. Attitude is no substitute for competence, and there's a certain basic toolkit of skills which you have to have before any hacker will dream of calling you one.
This toolkit changes slowly over time as technology creates new skills and makes old ones obsolete. For example, it used to include programming in machine language, and didn't until recently involve HTML. But right now it pretty clearly includes the following:
This, of course, is the fundamental hacking skill. If you don't know any computer languages, I recommend starting with Python. It is cleanly designed, well documented, and relatively kind to beginners. Despite being a good first language, it is not just a toy; it is very powerful and flexible and well suited for large projects. I have written a more detailed evaluation of Python, http://noframes.linuxjournal.com/lj-issues/issue73/3882.html. A tutorial is available at the Python web site, http://www.python.org.
Java is also a good language for learning to program in. It is more difficult than Python, but produces faster code than Python. I think it makes an excellent second language.
But be aware that you won't reach the skill level of a hacker or even merely a programmer if you only know one or two language—you need to learn how to think about programming problems in a general way, independent of any one language. To be a real hacker, you need to get to the point where you can learn a new language in days by relating what's in the manual to what you already know. This means you should learn several very different languages.
If you get into serious programming, you will have to learn C, the core language of Unix. C++ is very closely related to C; if you know one, learning the other will not be difficult. Neither language is a good one to try learning as your first, however.
Other languages of particular importance to hackers include Perl (http://www.perl.com) and LISP (http://snaefell.tamu.edu/~colin/lp/). Perl is worth learning for practical reasons; it's very widely used for active web pages and system administration, so that even if you never write Perl you should learn to read it. LISP is worth learning for the profound enlightenment experience you will have when you finally get it; that experience will make you a better programmer for the rest of your days, even if you never actually use LISP itself a lot.
It's best, actually, to learn all five of these (Python, Java, C/C++, Perl, and LISP). Besides being the most important hacking languages, they represent very different approaches to programming, and each will educate you in valuable ways.
I can't give complete instructions on how to learn to program here—it's a complex skill. But I can tell you that books and courses won't do it (many, maybe most of the best hackers are self-taught). You can learn language features—bits of knowledge—from books, but the mind-set that makes that knowledge into living skill can be learned only by practice and apprenticeship. What will do it is (a) reading code and (b) writing code.
Learning to program is like learning to write good natural language. The best way to do it is to read some stuff written by masters of the form, write some things yourself, read a lot more, write a little more, read a lot more, write some more ... and repeat until your writing begins to develop the kind of strength and economy you see in your models.
Finding good code to read used to be hard, because there were few large programs available in source for fledgeling hackers to read and tinker with. This has changed dramatically; open-source software, programming tools, and operating systems (all built by hackers) are now widely available. Which brings me neatly to our next topic...
I'm assuming you have a personal computer or can get access to one (these kids today have it so easy :-)). The single most important step any newbie can take toward acquiring hacker skills is to get a copy of Linux or one of the BSD-Unixes, install it on a personal machine, and run it.
Yes, there are other operating systems in the world besides Unix. But they're distributed in binary—you can't read the code, and you can't modify it. Trying to learn to hack on a DOS or Windows machine or under MacOS is like trying to learn to dance while wearing a body cast.
Besides, Unix is the operating system of the Internet. While you can learn to use the Internet without knowing Unix, you can't be an Internet hacker without understanding Unix. For this reason, the hacker culture today is pretty strongly Unix-centered. (This wasn't always true, and some old-time hackers still aren't happy about it, but the symbiosis between Unix and the Internet has become strong enough that even Microsoft's muscle doesn't seem able to seriously dent it.)
So, bring up a Unix—I like Linux myself but there are other ways (and yes, you can run both Linux and DOS/Windows on the same machine). Learn it. Run it. Tinker with it. Talk to the Internet with it. Read the code. Modify the code. You'll get better programming tools (including C, LISP, Python, and Perl) than any Microsoft operating system can dream of, you'll have fun, and you'll soak up more knowledge than you realize you're learning until you look back on it as a master hacker.
For more about learning Unix, see The Loginataka, http://www.tuxedo.org/~esr/faqs/loginataka.html.
To get your hands on a Linux, see the Where can I get Linux page, http://linuxresources.com/apps/ftp.html.
You can find BSD Unix help and resources at http://www.bsd.org.
I don't really recommend installing either Linux or BSD as a solo project if you're a newbie. For Linux, find a local Linux user's group and ask for help; or contact the Linux Internet Support Co-Operative, http://www.linpeople.org. LISC maintains IRC channels (http://openprojects.nu/services/irc.html) where you can get help.)
Most of the things the hacker culture has built do their work out of sight, helping run factories and offices and universities without any obvious impact on how non-hackers live. The Web is the one big exception, the huge shiny hacker toy that even politicians admit is changing the world. For this reason alone (and a lot of other good ones as well) you need to learn how to work the Web.
This doesn't just mean learning how to drive a browser (anyone can do that), but learning how to write HTML, the Web's markup language. If you don't know how to program, writing HTML will teach you some mental habits that will help you learn. So build a home page.
But just having a home page isn't anywhere near good enough to make you a hacker. The Web is full of home pages. Most of them are pointless, zero-content sludge—very snazzy-looking sludge, mind you, but sludge all the same (for more on this see The HTML Hell Page: http://www.tuxedo.org/~esr/html-hell.html).
To be worthwhile, your page must have content—it must be interesting and/or useful to other hackers. And that brings us to the next topic...