Generally concrete slabs should have a construction joint approximately every 8' x 8' area to reduce the stress on a slab and reduce cracking that accompanies larger poured areas. A construction joint is typically a 1" x 4" treated wood used as a separator between slabs. Scoring should be added at regular intervals across the slab before it cures, this will 'guide' inevitable cracks that develop over time. In the pictures shown here this patio and walk has an 8" space at intervals to later install a brick inlay.
There are two ways to reinforce the concrete mixture to insure that there will be minimal cracking during the life of your patio and walk. One is to add steel reinforcing bars or mesh and embed this metal into the liquid concrete. This is the most common way to make concrete stronger and minimize cracking. Another popular way is to request fiberglass entrained concrete straight from the concrete manufacturer to be ready to use when delivered. Although it will cost a little more it has been shown to be a reliable way to add sufficient tensile (bending) strength to a finished and fully cured concrete slab.