The German market is special. That's why you need a German SEO specialist to enter it.
German SEO means writing in German, having a German domain name (.de), a German server, links from Germany or German sites from abroad, e.g. Austria or Switzerland.
Above all German search engine optimization means optimizing for Google. Google dominates the market as a monopoly, having 90%+ market share in organic search.
Social Media like Digg, Delicious or StumbleUpon haven't been adopted in Germany. German users of Twitter and Facebook are still not enough to increase traffic significantly. So you have to come up with creative ideas for German SEO.