I can offer a little advice from experience, as our soil is naturally heavy clay with stones, and then more stones.
1. Take heart: clay soils are usually very fertile
2. If you decide where you will create paths/beds, you can void walking on the "bed" areas, and still get access to other areas of your plot
3. Compost everything possible. Millimole mentioned a compost bin: we have three made from pallets and they are invaluable
4. Try to get some rotted manure from a farm or stables, stack it and cover it until you can use it. The way forward is adding organic matter to the soil
5. Cover the areas where your growing areas will be with black plastic or light-proof tarpaulins as I will help weaken weed growth (we left some on for a year in one place, and everything under it died, and the ground was easily dug over
6. Consider all models of growing: lots of info on this site in the articles under the buttons at the top of the page: useful when it is too cold or wet to get out
We have slightly raised beds, which helps a bit with surface drainage, but any areas not being used to grow crops are covered with weighted down black plastic , which prevents nutrients leaching and helps keep it drier through the Winter. Lots of ways to organise your plot though!
Hope that helps a bit