From having been in several hunt clubs, I've learned there's a number of ways you can plant food plots and most of them will work ok to pretty good. I now have my own tract of land to hunt so I can do it my way and here's what works for me.... First of all, I only plant fall food plots, so this mainly applies to fall planting, although it should work for Spring too (just never tried it). Usually about late August I'll go in with my C-tine cultivator (with 6 spring tines) and make 2 or 3 passes and work the dirt over pretty good. FYI, a C-tine cultivator is not considered a primary tillage tool, but it works well for me since my plots have been worked over pretty good for several years now.
I let it sit for two weeks or so, then I will come back with the disc harrow and make 2 or 3 passes. By this time, most of the "large" dirt clod should be busted up pretty good. The next thing I do is to come in behind that with the cultipacker and pack the dirt down to make a firm seed bed. Then I will spread out the fertilizer and run the cultipacker over it again, to press the fertilizer in good.
At that point, it's ready to be seeded. I usually try to put the seed out mid to end of September because our rifle season opens 10/11 so I like to be done with the tractor work by then. Usually I try and time seeding the plots with the weather and put the seed out just before some rain is predicted. After I put the seed out, I will go back over it with the cultipacker one more time and pack the seed down nicely.
For 4 years now my plots have come up very nicely and looked really good, as long as they get sufficient rain. If you want some pic's I can show a few. I've seen the food plot planters and they are EXPENSIVE as heck. There's a used Frontier food plot planted on my local craigslist right now for $4800 dollars!! IMHO for that much money, you can buy the separate implements and do just as well, and have money left over, although it may take a bit more time as you have to do the steps one at a time. Planting food plots is my FAVORITE thing to do with the tractor, so I enjoy taking the extra time to do it right.
I strongly recommend a cultipacker though, you'll get really good seed germination rates with that. I remember in a couple of the clubs I used to be in, we would cover the seed up by running the disc harrow back over it, and I know a lot of the seed was getting buried way too deep to ever come up and they were just wasting a lot of money! Don't forget about getting soil samples done to tell what nutrients and fertilizers you need to apply to get the proper PH.
One last point... if you look at food plot planter, they usually have a set of spring tine cultivators in front, then a single gang disc harrow, then a seed box to drop the seed, and lastly a roller bar which serves as a cultipacker. If you will notice, that's exactly the same implements and the same order as what I use. Also, I have a rototiller but have never used it for food plots, just haven't really wanted to change what works, but maybe one year I will try using the rototiller in place of the cultivator and disc harrow. Good luck with whatever you decide.