Developing a healthy lawn all starts off with your soil. If the soil under the turf is good, you will have a healthy lawn for many years to come. For optimum growth, turf grass needs just four things (within the proper balance) to grow... sunlight, air, water and nutrients. Reduce any of these, or provide an excessive amount of any on and the grass may suffer or quite simply die. In the right proportions, the lawn will flourish.
Grass obtains three of these four essential factors (air, water and nutrients) from the soil, but many soils are less than ideal for growing grass. Some soils contain excessive amounts of clay and might be very compacted... just the thing for roads, bad for grass, because air and water aren't offered to the roots and naturally the roots can't grow.
Other soils can have too much sand... beautiful on a beach, but challenging to grow grass because water and nutrients won't remain in the root zone for long enough for the plant to use. Another frequently observed challenge with many soils is that it's pH (the degree of acidity or alkalinity) is too high or too low for optimum grass growth.
So getting the soil right is key. Idealy one would have the existing soil checked by way of a soil scientist, and he would inform you of what it needs, but this is not always practical. Simply google soil laboratories and you'll find one. Apart from getting advice from a soil scientist, there are basic methods that may be used to prepare the soil. Making sure you pick the correct method depends on your budget, and the condition of the soil to start with.
First you have to kill any existing grass or weeds with Glyphosate. Spraying once will kill most things, however if you can, a follow up spray a couple of months later is going to make sure virtually everything is dead. Before Spraying make sure the weeds and undesirable grass is healthy, it even helps to water a number of times before spraying to make sure of it. Round Up works better when the weeds are growing well.
When you are lucky enough to have good soil, then simply hire a subcontractor with a tractor rotary hoe, or hire a small one from a rental company to loosen the soil bed to (at the very least) 100mm, and a maximum of 200mm. In case the soil is too hard water it well the night before. After rotary hoeing rake out any dead foliage as necessary, and level the ground.
When the soil is of a clay type, or a sandy type, or relatively poor in other ways, buy some organic soil conditioner. Use a minimum of 2 cubic metres per 100 square metres. Spread this on top of the soil. If it is a clay type use Gypsum also. Use a rotary hoe to combine this well into the ground, after which rake the ground smooth.
Hiring a skid steer to perform the work is another method. If you'd like to get a contractor to do the preparation it makes life easier. Make sure the operator rips the existing soil well first, loosening the base. A hard compacted sub soil is the last thing a lawn needs. Then order 7 cubic metres of good quality organic soil blend per 100 square metres or ground. Ensure it has a decent amount of organics in it. Spread this with the skid steer, making sure the finish is smooth. In some areas you may need to rake smooth with the back or front of a rake.
Turf is the safest and best way to install a lawn. Laying turf is really easy. Seeding only works well in places like Tasmania where cool climate turf like Fescue is used. For Warm climate turf like Buffalo no seed is available, and for Couch and Kikuyu, the seed germinates very slowly, and it is difficult to get a good result out of.
Simply lay one roll around the outside and then fill in the area with the turf all going one way. Patch up any gaps, roll the lawn if you're able to, and water in well. On hot days water the turf in sections as you lay it. Don't fertilise till a month after the turf is laid. University research proves that turf receives no benefit from fertiliser until a month after laying. Then make use of a good slow release type.
For the first 2 weeks the lawn cannot dry out. On a hot day in summer that may mean watering 3 times per day, or on a milder day once per day. After 2 weeks watering can often be reduced to every 2nd or 3rd day.