Assembly of your products can be enhanced by following a few simple guidelines during the design phase of a PCB.
Remember, operators must be able to handle your board during production. This means small boards should be in a panel having at least 1/4" of frame. This not only allows handling but also mounting in machines. Components can be closer to the board edge when in a panel.
Larger individual boards without frames must have components no closer than 0.050 inches from the board edge to accommodate mounting and handling.
Insert alignment targets in the upper left and lower right of your board. Alignment targets are created using either a 2mm circle of metal without soldermask over it or a butterfly pattern made up of two 1.5mm squares without soldermask. The alignment targets should be spaced from hole or other geometries by about 2mm if possible. I recommend that each board in a panel have it's own targets to allow for flexibility when placing components. The panel may have it's own set of targets as well.
Minimize cost of assembly.
SMT parts on one side of a board is lowest cost to assemble.
SMT and Through hole on the same side are the next level of cost.
SMT on both sides is the next higher cost.
SMT on both sides plus through hole on one side is higher yet.
SMT on both sides and through hole on both sides is the most costly to assemble.
The reason is simply the number of operations required to complete the job. Each more complicated level requires more operations, operators, equipment and mostly time.