Easiest way to get a signature is to request it from our GFX Team Here: http://forum.infinitymu.net/showthread.php?20751-Request-Area-Nocturnal
Just give your render text subtext and Size and you can get a really good siggy.However if you dont like it you can make it yourself from the suggested ways above
Firstly you have to download Adobe PhotoShop (any version) but i preferr you CS4. Then for tutorial's and PS stuffs you can visit www.gfxresource.com . That's a forum from where you can learn everything about Siggy making.