On returnable fuel engines (not sure about returnless), there is a Schraeder valve on the fuel rail - looks just like the valve on your tires, because that is a Schraeder valve as well. I had trouble finding the one on a 96 Zetec (but eventually found it), and the Duratec's is pretty much right under the accordian tube IIRC.
Just go into any parts store and ask for a fuel pressure gauge. Make sure it has the adapter for a Schraeder valve (it'll probably say "for Ford vehicles" or something similar on the packaging.) IIRC I paid $20 for mine.
Pull the cap off the valve and put the gauge on. Careful - you're messing with gas now and a little will escape. Start the engine and let it get to a steady idle. Read the gauge per the instructions with the gauge. The idle pressure should be right at the spec Lance quoted.
And now you know how to use a fuel pressure gauge.
