Question
My son just purchased a new home and he wants to plant grass seed in his backyard. He has sod in the front and on the sides. His backyard is bare ground with some spotty weeds here and there. We are trying to keep the cost down as much as possible. I suggested to him the following.
?  The ground is a little uneven and a bit hard. I suggested renting a dethatch machine and go over the entire yard to loosen up the top of the soil.
?  Then possibly put down some type of nutrient for the new seeds (any suggestions?).
?  Not sure what would be the best seed or amount needed.  Any suggestions?
?  The put the seed down with a broadcast spreader and go over it lightly with a rake to cover the seeds slightly.
?  Then put a thin layer of straw over the yard and water.

Specs on yard and location:  Located in central Illinois. Yard is about 6,000 sq. ft. Any suggestions or comments to the above would be appreciated.  

Answer
You don't want a dethatcher, you want a tiller.
Thatch occurs when grass roots come to the surface, die and trap other debris and make a thick, waterproof pad that will not allow water or anything else to soak into the soil.
I would rent a tiller, till up the soil and add cedar bark mulch, some humus and peat moss, and till it all together.
That should loosen up the soil nicely.
Check the soil by putting a spade in it and digging a hole about 6 to 12 inches deep, to see if it has a lot of clay, or is just hard from compacting.
If it is nice loose soil, just tilling it up will be enough without adding the bark mulch.
Peat moss and humus are still good to add, because of the nutrients in them.
After you plant the seed, apply sugar to keep benificial microbes alive. these microbes enrich the soil, and weeds do not grow in rich soil.
I use 1 pound sugar per 250 to 300 sq.ft of lawn.
Water in well, to a depth of at least 6 inches.

If you dig down, and it is hard, compact clay soil, write me back and I will help you determine how much bark mulch you need to ad.
I use cedar bark mulch, because it repels so many insects, including termites, fleas and ticks.

I don't plant grass seed. st augustine is what I have, and I sodded it in.
I place the sod pieces about 6 inches apart, and they spread together very fast.
Any grass that puts out runners will spread and fill in the bare spaces.

After you have it tilled up, you might want to rent a mching to roll over the yard and pack the soil down a little, or you can juet scatter the frass seed, and I am not sure if you are supposed to rake it over with soil, or just leave it on top of the soil. Putting down enough straw to hide the seeds from the birds is a good idea.
I always water to a depth of at least 6 inches, to encourage a deep root system.
A deep root system helps protect against heat, cold and drought damage.
I rewater when they top two inches are dry.
Shallow watering is the biggest cause of thatch buildup.
the roots have to come to the surface to get water.
anyway you feel I can help, write anytime.
Charlotte