Advice, start simple, say DVD/CD player, as this type of device doesnt use many buttons, and once you have the buttons working start playing with custom buttons, macros, menus etc etc.

Try downloading a few of the sample ccfs from this site and just play with them in iProntoEdit and learn how people link buttons/screens etc.

I tend to have a hidden screen with very simple monocrome buttons that I then use the pronto to learn the codes from my remote, I then have a visable fancy screen with allt he bells and whistles, this then references the buttons on the hidden screen, that way if I wan to play with the layout I dont have to keep learnign codes. This was one of the biggest lessons I learnt with my old mono ProntoBrick!!!

It will take you at least a month of constant playing before you start to feel that you have a design you like, and then you'll keep on tinkering with it!!!