This is what my physio told me to do:
Calf stretches
Stretches for the plantar fascia - stand with the balls of your feet on a step. Slowly drop your heels down so you feel the stretch in your calf muscles and plantar fascia, then slowly raise them up again. Repeat 10 times several times a day.
Massage - warm up the PF by putting your feet on a hot water bottle (don't stand on it, obviously!). Then roll a golf ball around under the arch of your foot, or one of those wooden foot massagers, or simply use your thumbs.
Worked for me!