It sounds like your plot is ideal for a four part rotation system. Since you are starting from scratch, and the plot has been fallow for over a year, then it doesnt really matter where you place your various groups, although you may prefer to site things so that your onions and potatoes dont coincide with those previous beds. However, you will find it easier if you have a book to help you, I dare not suggest any particular one, but a general vegetable gardening book would be a good start, particularly with Christmas coming up...
My advice is to remember to enjoy it ...
Derekthefox :D