I have witnessed shoddy preparation on many occasions over the years and I believe that the appeal of one minute having a dark brown look and the next a bright emerald sheen, tends to make customers ignore proper preparation.
The popularity of TV gardening programs has led to an array of celebrities giving out advice on subjects that quite honestly they have no real knowledge.
The preparation of a lawn for turfing needs to be carried out in the same meticulous way as you would to prepare a seed bed.
If you have a small area then double dig your plot and incorporate some organic matter to give the soil some body. If you are in a heavy clay soil area this task may be exhausting but it will surely benefit your lawn as it develops.
Incorporate some sharp sand as you go making sure it is ameliorated into the full depth of the worked soil so that the fine particles of clay are interrupted evenly by the large grainy gritty sand [be sure of your source - any material that is excavated in coastal areas will contain salt and can contaminate your soil. Salt causes ex osmosis in plants which is exactly the opposite of your requirements].
Clay, whilst a great medium to grow into, is also a poor conductor of water and heavy rain will quickly clog the closely packed tiny air spaces causing water logging. Capillary action pulls water tightly against the soil particles making drainage (hydraulic conductivity) difficult.
If you have a large plot then turning to a rotovator may be required. A necessary evil but on a clay soil the paddles of the machine may cause smearing or polishing of the clay as it rotates. In doing so this could lead to an impermeable layer below the surface adding to poor drainage so be careful that you do not overdo it and make sure that the plot is dry enough before you start.
Your soil is best left to weather for a little while to naturally break down but if time is not on your side then begin breaking down the clods. A fork with large times or a rough rake will do. Repeat this process until the soil has broken down and remove any stones larger than 10mm and any grass that comes to the surface.
Levels can be hard to get right but a little diligence here will bring satisfying results. If you already have a hard edge like a pathway then you are well on the way, if you do not have a hard reference then using simple pegs and string is the easiest way.
Rake the soil out so that the tops of your pegs are level with the soil surface. Once you are content that this is right then it is time to tread the soil. It is best to where a pair of sturdy boots with a defined flat heel. Walk across the soil but do so on the heels only. This will ensure compression of the soil and help break down the soil even further. Do not stamp but firm only and make sure that the process is continuous and you do not leave space ensuring good coverage.
Now we are onto the nitty gritty. I favoured a hay rake with wooden dowelled tines (even better if slightly rounded at the tips). The head of this rake is about 60 cm wide and it helps to keep the levels right. Too narrow and the head digs in. It also takes longer.
Use long drawn out sweeps. Imagine a rower with good timing. Rake out to a fine tilth until you are happy with the results. Ensure you work backwards so that you exit your plot without standing on the prepared soil.
Apply a base dressing fertiliser. A growmore 7-7-7 artificial is good but if you want organic you need to use an alternative product.Source good quality turf to give your lawn the best start.
Lay a single row of turf out to form your border. This gives the shape but also creates an edge to cut to which is much more economical than throwing away the ends.
Once the turf is rolled out in your first row, use a scaffold board to act as a walkway. It serves two purposes. Firstly it will give something to walk along and also act as a tamper without excessive compression.
The new turf needs a combination or air and soil in which to establish without too much resistance. The board will leave the conditions below ideal.
Use a sharp half moon to edging iron (this is often erroneously labelled as a turfing iron. A turfing iron is a different tool altogether and was/is used for lifting turf before the invention of machinery and is still used today to lift small areas when repairing a golf green for example.
Do not be wasteful. Cutting turf at an angle to your border will often mean the leftover part will turn around and start your next row as described in the illustration.
Click on illustrations to enlarge.You might find this post interesting - Preparing your soil for turf or seed