Collecting of medals has always been fun to me. As a rather young hobby it has quickly gathered fans and collectors all over the world. Decorations have always been part of numismatic auction, but started to get broader attention during the 1950th when especially the GI's were looking for war souvenirs. Very reputable collections were built during the last century, some still being on display in the US.
As many other collectibles the medals have experienced an extreme increase of their value. Forgers have certainly not wasted any time to infiltrate the market with fakes. As a new or beginning collector it is imperative to join local societies and read about your new hobby.
To find good reference material you should try to copy the following line fo key words into Google:
imperial german orders medals decorations
The very first link medalnet will give you hundreds of articles about this topic.