I don't think you would need to go the weed killer route as clover once it gets rooted will compete nicely with most native weeds in your area. I would mow the field as low as you can and then disk it well. It might be a good idea if you don't have a pulverizer of similar attachment.....something like this one shown here: (
BEFCO - Products - Ground Engage Equipment - Soil Pulverizers ), To attach a weighted board or timber behind the disk on the last few passes through the field and this will help level out the dirt and hopefully mash down and smooth over most large clods and clumps and leave a nice smooth surface.
I wouldn't worry too much about adding fertilizer to the field at this point, if that is you are only planting clover because this will benefit the other weeds more than the weed you are planting. You need to fertilize the clover patch only after you see a couple leafs appear on the newly sprouted plants and a liquid type would be best for this.
You would however want to put down fertilizer if you are planting a mixture of clover and other grasses and I would check the PH level of the field and you will most likely have to add lime. I would add my lime after you mow the field and disk it the first time, then let it sit for a week or two to let the old vegetation dry out and die and also to give the lime a chance to start to work.
Depending on how you plan on seeding the field, by a hand seeder or one that attaches on to the PTO on the tractor I like to mix the seed with dry course sand to help distribute the seed evenly throughout the field, the sand helps to hold the seed in the hopper to keep it from pouring out too fast and putting down too much in spots. Even the smallest setting on most seed spreaders is too large for clover seed.
The sand seed mixture is only needed if you are planting clover seed only. If you are planing on putting something else in the field along with the clover like Annual Rye or some other type grass just mix it well with the grass seed and you should be fine. Once it is planted I like to go back over the field with a light drag, you don't want to dig into the soil, just drag over the top to help distribute and cover the seeds somewhat. A piece of old chain link fence about 8' or 10' sq. dragged behind the tractor works great for this.