Stretching. I do a stretch where stand with my feet shoulder width apart, I point my toes in at about a 30-45 degree angle, then bend at the knees keeping my back straight. I can feel the "pull" up the back of my calf. Hold the position for a count of 10, then relax for a count of 10, then repeat. I repeat the sequences 10 times and I do it 3 times per day. It's sort of like a skiing position.
Wear good shoes with high arch support. I do Crocs and Birkenstocks mostly.
If it gets really bad, anti-inflammatories work, as does rolling a frozen water bottle under your foot. Rolling golf balls under your foot helps too. My DH got me a foot massager one year for Christmas that has a sibrating action and a Shiatsu ball. Let me tell you, when it is acting up and you put your foot over that Shiatsu ball, at first it nearly sends you through the roof with the pain, but after about 2-3 minutes, the relief is amazing.
I had my PF treated for a while by a podiatrist. He would inject my foot (which hurts like heck!!!!!!!!!!!) with a non-steroidal anti-inflammatory and then strap my arch by padding the arch really well with gauze and then taping it up around my foot and also taping the foot in a slightly flexed position. It's a pain, but does really help the discomfort.
PF is no fun!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!