It's all about the prep. The ground must be graded properly and compacted with base rock. Connect your rain gutter downspouts to an underground pipe and divert them into the storm water drain. Make sure your concrete patio does not interfere with the natural drainage of the soil; put in underground drains to allow for the rainwater runoff.

The lines trowled or cut into the slab are called control joints. These are where the slab is supposed to crack. Have your contractor design plenty of control joints into the pour, to avoid cracks where you don't want them.

Mist water on the concrete as it cures, especially in the hot sun.