There is no step-by-step guide on how to make skins, but there are a couple of guides to help you get started, that cover recolouring of graphics etc...
Your best bet is to start with a skin you like and edit its files slowly, seeing what each bit of code does, several of the xml files for the game and skins have commented lines in them that give you a basic idea of what the block of code relates to.
You should also scan through previous posts on this forum, some of them have extensive help on how to move bits of the skin around etc...
Also have a look at
http://smithjurdskins.co.uk/ and
http://sortitoutsi.net/ aswell as there forums, there's a couple of simple guides that should get you started.
Other than that its trial and error (that's how I learnt/am learning when I get the time.)
If you have a specific question do a search to see if its been asked before, if not hopefully someone will answer if you post what you are trying to do in detail(i.e. moving the position of the logos.)
If something has been done before in another skin, your best off looking at the xml files for that skin to see how that author did the changes (not that this is always that helpful)
guide to create a skin 
Linear Mode
