Concrete Alberta recommends the following site preparation tips for placing concrete:

• All black dirt, vegetation, wood, bricks, large rocks, etc. should be removed and the site leveled off.
• The base should be uniform, preferably undisturbed subgrade soil. A granular base is usually not necessary, however, crushed fill of 20mm maximum size base coarse material may be used to bring the site to uniform bearing and final grade. Backfill material should be well compacted.
• The base should be dampened before the concrete is placed.
• Forms should be constructed with 50mm normal thickness lumber and should be well anchored with 25mm X 50mm (1 X 2 inch) stakes, driven firmly into the ground at 1 metre intervals.
• Forms should be oiled before placing the concrete to facilitate form removal. Slab thickness should be a minimum of 100mm where the driveway is to be used exclusively by passenger cars. If larger vehicles, such as trucks with topsoil or moving vans, will be using the driveway, a thickness of 150mm is recommended.
• Reinforcing steel is recommended, but not required.
• Reinforcing steel does not prevent crack formation, if properly placed it can reduce the amount of control joints required in your concrete stab.