I started out with a seven year rotation but have settled for a six year rotation because I have set aside one whole bed for comfrey, nettles and alfalfa as a permanent green manure cutting bed.
My six beds go as follows:
Year 1 the bed gets a massive helping of homemade compost and in spring I set out my potatoes on top of this and put layers of straw on top to shut out the light and give the spuds something to grow into.
I follow potatoes with a green manure that will over-winter but hoe off easily for next year - something like winter tares.
Year 2 the compost and straw have rotted down and in early spring I hoe off the green manure. The bed is now firm enough for onion sets and garlic, which I start off in modules and plant out. Leeks and spring onions also go in this bed.
Onions are followed by any plants I want space for so long as they are not Brassica as it is good practice to keep brassica years apart by at least three years.
Year 3 is for Peas and Beans. These will fix nitrogen, which will be great for next year.
If there is time, I will sow an over-wintering green manure of alfalfa or winter tares to increase and hold onto nitrogen over winter for next year.
Year 4 and the bed is firm as I don't dig if I can help it and I didn't need to dig after Peas and Beans - I just hoe them off. Year 4 is Brassica and these will benefit from the nitrogen fixed in the previous year and over winter.
Year 5 - this bed will now be for Carrots, Parsnips, Beetroot, Fennel, salad crops and miscellaneous plants.
Year 6 and the bed is ready for a good meal by now - a heavy helping of compost which is laid on and left to cook over winter after bed 5. Here I plant squashes, pumpkins and Sweetcorn with climbing beans clinging onto the sweetcorn and sticks I drive into the bed for support. The squashes provide good shade to keep watering to a minimum for the sweetcorn.
Now the bed is deep in composted material, more is piled on this winter ready for potatoes all over again and so on.
Year 1. Potatoes
Year 2. Onion family
Year 3. Peas and Beans
Year 4. Brassica
Year 5. Miscellaneous
Year 6. Three Sisters
hope this helps - works for me but a lot depends on where you live and what soil you have and other factors.