I don't know if Walter T Kelly sells it anymore, they should, but couldn't find that info. Here's a link http://www.outsidepride.com/catalog/Yellow-Sweet-Clover-Seed-p-16706.html
You will need to talk with whomever you buy the mix from as to soil requirements.
I planted 3 different types of clover on my property going on 3 yrs now. Two white varieties and a red one that are doing just terrific.
My buddy did all the leg work cause he's the one with the Kabota. We started off by mowing down the 1 and 3/4 acres we planted, I did this with my Sears tractor mower I bought from the previous land owners for a hundred bucks!
Next he disked everything up and then drug some thing that gathered up most of the grass and we put that off to the side.
We made piles of all the grass clumps I removed by hand with a rake, it was a lot of work, but my buddy is particular and said we needed to get rid of all the grass.
Next he ground up the earth with his various attachments and then we added a bunch of bags of lime, then the seeds I believe, then the fertilizer and mixed all this together and buried it all.
It rained within a day or two which was ideal. Like any crop its good to plant when rain is approaching.
We actually planted other stuff as well, buck forage oats and winter wheat. This was for the deer.
He said the clover wouldn't really come up til the spring (we planted in the fall).
He was dead on about everything. In the spring I went back and cut all areas and threw out some 0-20-20 fertilizer, remember this mix, you will want to re-fertilize with the 0-20-20 occasionally.
What it does is fertilize the clover but it doesn't fertilize the weeds, isn't that nice!
The clover grew up but not the weeds, I cut it every now and then for new growth.
It is now going on three years and except for a little cutting and fertilizer it is going strong.
I put some bees near a patch last weekend and will be putting out more hives.
Here's a few pics