Try the lawn forum for some good advise

Well, it really depends on how extreme you want to get. I just replaced my entire south lawn as I hated the original, it was uneven and every summer patches would die, while in the winter other patches would become mushy mud. It never looked good. Name a season and I could name the affliction instantly! After dreaming about the perfect lush green lawn I knew that I had to do it right.

First of all, you must pick the right grass seed. From what I have discovered too many people just buy a box of discount seed off the shelf and don't think about it. Grass comes in many types and can be planted in combinations. Some like shade, some like full sun, others like damp while some thrive in dry soil. Be sure to plant the correct type for you climate and location. Also pay attention to the durability, some grass will wear out fast if you walk on it often. I carefully browsed the different types for some time before making a choice, but I think it was the right one as my lawn looks great now and there's not a bald patch or slushy mud pit anywhere in sight!

You also need to do extensive preparation work for the best results. I dug over the area several times and mixed in water saving polymer crystals (I don't have sprinklers and wanted some drought protection). I also included a few bags of cheap compost as it would feed the lawn for a few years and radically improved the dense soil texture. Finally, lots of sand. For some reason grass loves sand? Golf courses use sand a lot and a number of the seed boxes suggested I use sand. Now that I think about it most the grass I see growing in the wild is in a sandy soil, I guess it's just helping make the environment closer to it's native one.

Finally I fitted a good quality metal edging and made the soil surface as smooth and relatively flat as possible. I personally despise ultra-flat 2D lawns as they bore me, I like to have gentle flowing curves that bring to mind a golf course or an older lawn to match an old house. It looks good to me and seems to suit an older house, but whatever effect, either gentle slopes or totally flat you aim for, be very careful to compact all but the last inch or two of soil as freshly dug soil will settle a lot once you start walking on it. What started out as a flat lawn can become very bumpy if you don't. After this seed and wait.

I did go for the most extensive solution to the problem, but I wanted the perfect lawn that would look good all year. I figured the difference between a perfect lawn with premium quality installation was not a vast price difference, but more hard work and research. Still, I think it's worth it as a bad lawn detracts from the entire garden and will cause more frustration over the years while consuming more time/money to reduce it's problems. I know too many people who like I used to, spend a fortune in time and money applying chemicals, weeding, patching and reseeding a bad lawn only to get second rate results, when really they need to replace it for both the results and to stop the futile repair cycle to keep a rotten lawn presentable. You may as well do it right the first time.