Taping heel spur or plantar fasciitis can be a very effective method to treat the injury. Also it is a relatively cost-effective way of treating fasciitis.It can even be used to prevent plantar fasciitis when severe strain is expected, like in sports, or mountain walking.
There are some drawbacks and risks which need to be considered. Occasionaly there are reports of ankle pain and achilles pain through use of tape, and also some people have an allergic reaction, though proper athletic tape can minimize this risk. Note that taping is therefor best done by a skilled therapist. Wrongly applying tape can have negative effects and even cause more problems then you already have!
So, how does it work? One of the problems with fasciitis is the constant tension on the plantar fascia. Applying tape can assist in relieving this tension by limiting the extent how far the fascia can stretch, thus preventing over pronation.
The goal of the treatment is to apply tape in such a way that the fascia cannot over-stretch, thus preventing further damage to the fascia and it's attachment to the heel. Applying tape should preferably be done by a professional at least the first few times, as incorrectly placing the tape can cause an opposite effect. Also make sure to use specialized tape for this that doesn't damage the skin (no duct tape...). It also helps to clean the feet properly before applying the tape (also dry them very well!).
The usual way to apply tape goes as follows: Separately cover the ball of the foot and the heel with tape and then connect the heel to the toes using a criss-cross taping pattern until the whole sole of the foot is covered.
See also this video (courtesy of sportsinjuryclinic.net):