At the beginning, you should specify how big the surface which you want to pave will be and what maximal strain shall be placed on it. This is exactly the size and thickness of material that should be used in that place.
While planning the arrangements of the surroundings you should resign from placing small paving blocks on big areas such as driveways and small squares. Big blocks should not be cut and forced onto small, narrow pathways. A much better effect will be achieved by selecting a size appropriate to the space.
The thickness of the material should be selected carefully and should correspond to the strain of the traffic. On alleyways and garden paths used for walking, the 3-4 cm tiles work great just as the blocks that are 4-6 cm thick. The driveways to the residence and the driveways into garages require stronger solutions. There, in the places where you expect automobile traffic, pick blocks that are 6-8 cm thick.