stalling Pavers gravel vs sand
The proper way to install pavers is to have a base compacted suitably for the use. The compacted base surface must be parallel to the finished paver surface. Most pavers are 60, 80 or 100 mm thick.
Spread a 1" later of sand on the base and screed it off smoothly. The sand should NOT be thicker, should NEVER contain cement and is NOT compacted. Concrete sand is ideal.
You should also have an edge resratint (plastic, aluminum, steel or concrete).
Lay the pavers with tight joints and sprinkle fine sand (masons sand or fine concrete sand) over the pavers. Compact with a plate compactor (can be rented) and sweep off the excess sand that does not vibrate into the joints.
This is reaaly the only method recommended for interlocking concrete pavers (the most common type of pavers used). The main variable is the strength/compaction of of the base and possibly the paver thickness, although 80 mm pavers are acceptable for most apllications. This method is recommended for pavers installed for patios, sidewalks, driveways, streets, airport taxiways for 747s and industrial pavement applications.
For details on the selection, planning, installation and maintenance of pavers, go to the Interlocking Concrete Paving Institute site - icpi.org, I believe.