[bestgenman]

Here is a personal take on fuel pumps and filters.  It differs from many manufacturer's position in that many primary filters are installed on the suction side of the lift pump.  This is to protect the pump from debris as it's suction is from the tank generally.  My opinion is; there should be a strainer only on the suction side and the primary & secondary filters on the pressure side.  The reasoning is because it is so easy to draw air on the suction side which leads to so many fuel system problems, including low fuel pressure.  Yes, the strainer can cause air inclusion however,  it is not serviced as frequently therefore not as problematic.   

As Richard says, a fuel pressure gauge on the pressure side gives a quick visual of system pressure.  I hardly ever change the secondary (annually changed)  since the primary,  Racor in my case, receives the brunt of dirt and water.