First get Skin Studio, then USe your imagination and get lots of ideas then make sure you have a ghraphics editor like photoshop or paint shop or something similar, next try opening one of the skins you have in skinstudio and editing the graphics and such until you have it the way you want it. This is only one way, there are others like just makeing all the graphics in photoshop and applying them to a skin but it is tough unless you know what you are doing because you need dimensions and such of the graphics.

P.S. If you alter a skin make sure you make it different from the original skin enough so to call it YOUR skin .... if not you need permission from the original author if you are going to upload it and share with us.