Expanding upon what Joe said:
1) Turn on the Master Switch, listen for the electric fuel pump clicking and slowing down as system Fuel Pressure (FP) builds up, and look for @ 3 psi on the FP gauge. If the airplane is heat-soaked, let the electric fuel pump run for awhile (a minute or two) to allow cooler fuel from the fuel tank circulate through the fuel lines.
2) Start the engine and verify that the FP gauge is now showing @ 5 psi (i.e., reflecting the additional pressure of the now working engine-driven fuel pump).
3) During run-up, verify that FP remains @ 5 psi. If you want to double-check the fuel pump system, momentarily pull out the FP circuit breaker and verify that the FP is @ 3 psi with the engine-driven pump alone. Typically, I do not see any reason to do this if the FP is @ 5 psi.
4) In-flight, visually monitor the FP gauge as you would other engine instruments. The SV/Garmin units provide an additional visual/aural warning if FP drops.
5) After landing, shut-down the engine and listen for the clicking of the electric fuel pump before you turn off the Master.
The "full-time" electric fuel pump as installed in a standard RV-12 keeps cool fuel circulating, helps to avoid vapor lock, is not likely to be forgotten, and apparently has a relatively long service life. Others may prefer a switch-controllable electric fuel pump ala many low-wing airplanes -- I prefer the Van's factory set-up. As a critical flight item, I carry a spare electric pump with pre-attached electrical connectors and AN fittings -- just in case.
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B) - N124DH flying since March 2014 - 580+ hours (as of Dec 2017)!
through June 2018.