To prepare soil ensure you have a good thickness of top soil, if you have a new house you may have very little topsoil at all and will need to enrich the soil. Sandy soil will require organic matter and clay soil will require gypsum. The soil needs to be well tilled to about 15cm depth and if you are importing top soil it should be a sandy loam and should be incorporated in the existing soil not just placed in to a layer on top. A Bushranger Cultivator can help you to till and aerate the soil to ensure the grass roots can penetrate. Ensure you have good drainage, if you have high clay soil or a slopping block you may need artificial drainage. To ensure good drainage, you can excavate an area fill it with rocks and then add top soil, talk to a landscaper if you require more information. Make sure you remove all rocks, stones and unwanted organic matter than may grow later. If you have any weeds dig these out or use an herbicide. If you have some existing turf cut it out and put aside to be reused. Level the soil using a shovel, spirit level and a long flat piece of wood. Before the grass is laid or seeded fertilize preferably with an organic lawn food such as dynamic lifter and use a wetting agent to keep roots moist, and then rake the soil to loosen it again.
Check the ph of your soil, lawn prefers a slightly acidic or neutral soil. You can buy a ph kit from garden centers or hardware stores. If the test is between 6.5 and 7 you do not need to do anything. But is you have 5.5 result or lower that means that you have soil that is slightly acidic and needs "sweetening." You can use garden lime or dolomite. Dolomite is preferred as it is high in magnesium and most Australian soils are low in magnesium. Gypsum on the other had is good for clay soils as it breaks up the clumps and makes it easier to work. Use one handful or dolomite or lime per square meter.
All lawns need an edge to define their shape and prevent grass from invading flower beds. It also helps retain moisture, to keep the lawn green longer, avoid the need for irrigation and makes mowing and edging easier. Mulch such as bark chips or cane mulch or pavers, sleepers or pine logs can clearly define where your garden ends and your lawn begins.