Always consider the potential for expanding the capacity of the system. Pipe friction loss charts assume new pipe with smooth shiny inside walls. Minerals in the water will often create a film on this inside surface. This rough film will tend to increase the friction loss over time. Extra fittings in the pipeline will increase the friction loss.
Air bubbles can collect in high spots in the line.
These can restrict water flow unless flushed out or released at the high spots using a valve. Many float valves are very restrictive to water flow. Use a valve that produces minimum back pressure. Watch out for competing water uses on the same water supply. Another stock waterer or the farm house will usually provide an easier place for the water to go if it is given a choice.