Answer:
There are two generally accepted ways to protect your springs. The first is to simply tape them up. Depending on what tape you are using (duck, electrical, hockey, ect) you might need to tape them several times. Usually three to four times is enough. It is one of the easiest and cheapest mods you can do to your stilts but their are drawbacks. Eventually after damage you'll need to re-tape your springs which can be an annoying, sticky mess. Another problem is you are taping your springs which can make a less then cosmetically appealing appearance.
The second option is spring armor. This is the method of fitting a bike tire over the springs and lacing them up. It can give your stilts a nice look and provides exceptional protections compared to tape. One of the major drawbacks to this is it is time consuming to do and requires a good amount of patience along with certain tools. Here's a site giving instructions http://www.stiltmodz.com/