The best thing is to take classes. But hey, I don't think that's something you want to do, do you?
It's a hard path, let me tell you. You have to be really creative. Software isn't everything by the way, you could technically be a pro with the software but still sucks at design. It's also quite a large domain, ranging from printed to the Web.
I would like to say that photoshop isn't the only app used. I would guess the 3 apps that are used the most are Photoshop, Illustrator and Indesign. It just really depends on what exactly you want to do. Photography editing+Complicated graphics? Photoshop. Logos+Vector drawing? Illustrator. Books and posters? Indesign. You should also consider a font managing program. Using only the system font folder can get quite messing when you're dealing with many different fonts that can significantly slow down your Mac for nothing. We're using Suitcase in my class. I completely hate it, but it's doing it's job. Adobe make one I think, called Font Book or something like that. Don't use it.
Like I said in another thread, the serie of books: "Classroom In a Book" are really nice. Great when you know nothing about the apps. They probably won't teach you a lot about graphic design itself, but you will be able to use Adobe CS. Just take into consideration that it is made for CS3 and not CS4, so some things might have changed between books. CS4 will be coming eventually, so just wait and see. They are also 50$ each, so I would only recommend to begin only with Photoshop, Illustrator and Indesign.
Two last things: First, try to search for design graphic blogs. That way you can see what it's currently being done by artists from this domain. Second, read this blog
http://www.yourlogomakesmebarf.com/. Great exemple of what you should not do.
And, hey, DON'T forget to NEVER use Comic Sans. NEVER.
