Hey and hello. Everyone skins differently, so advice is kind of hard to give. Speaking for myself, I got started by making up a 245x348 template out of .bmp files you can get by doing a skin search for "template." I took mspaint and cut and pasted together a full picture of Main, EQ, and Playlist. Once I had that, I used to lay out my skin the way I wanted it, run it through a skinner, and then edit all the files until it was right. This is a good way to learn because it teaches you what the various .bmps do and how the skin itself works.
A good thing to do when you are just learning is unzip the Winamp Base skin into a seperate folder somewhere so you can use it as a reference. (like which parts of the .bmp file are button up, button down, that sort of thing.) Another good beginning trick is download a kickass skin like "Major Tom" or "Zeus", unzip that into a folder, and check out how the .bmp's work against the functioning skin. Just dont rip.
Other than that, just get some good graphics programs and start experimenting. You can find demos, freebies, etc. here:
just do a search for "graphics editors" and grab a few that look good. Imageforge is probably the best overall freebie, in my opinion.
ps, don't feel bad about the skinner. It's a tool that you can use eventually just to take some of the donkey work out of skinning. (Don't tell, but I use a skinner for all my stuff.
) This was done using a skinner as one of the building tools:
Good luck and have fun!