Box with scarifiers will work, as per another post, but you'll sure spend a lot of time. A disc harrow (OK, a disc with some sort of dirt clod buster device trailing behind) would be fine, if the soil is soft, say after a few days of heavy rain (otherwise, the size disc that your tractor could pull won't penetrate the soil much - just too light). A tiller is the ticket, if you can rent one - buy one if you're going to prepare a large (1/2 acre plus) vegetable or whatever garden yearly.
Good luck (I've just come off a tractor after spending hours leveling trucked-in soil over a drainage pipe and wide, but too low, dam I created a few weeks ago - there is NO more boring task than distributing and leveling "fill" over a wide area - and then you have to distribute and level a layer of topsoil so grass will take and prevent erosion).