I try to avoid sowing some crops in the same place two years in a row...potatoes, tomatoes, brassicas, onions, garlic, shallots leeks for example as these are the "disease prone" ones.
Other, like carrots, parsnips, beetroot, peas & beans, squashes get fitted in around these, and I try to move them about each year as they take different nutrients from the soil, but sometime that isn't that easy so I do the best I can. Short term stuff like lettuces, summer radishes, spring onions etc go in where they can.
I aim for a for year rotation, with some follow-ons planned in, like leeks, dwarf beans, late brassicas, florence fennel etc but it never quite works and somehow everything grows OK as long as I look after the soil