For me, I initially learned via documentation on Netscape’s web site. That was back in 96 or so, but the developer network has come a long way since then. Oddly they list out the reference before the guide - I’d definitely start with the guide.
Lastly - don’t forget that all of this runs in a browser. If you’ve got a browser (and - um - you must) and a text editor that you have all the bare minimum tools you need. You may want to look at using Dreamweaver to help out - or the excellent Aptana editor as well.
Like most things - how you learn best is something you know. Books, online training, just playing, or a mix of all, figure out what works best for you and just make the time.