The key part of German potato salad for me is the lack of mayonnaise and eggs. I make this up from scratch whenever I make it, but my version always includes two essential ingredients: Dijon mustard as part of the vinaigrette (I like the flavour and tang that it adds) and finely chopped dill pickles (a satisfying crunch and burst of vinegary / salty goodness).
I also usually put in bacon / guanciale / schinken speck, but this time around, knew that there were going to be a number of vegetarians present and skipped the meat products. Hence, I (*gasp*!) accidentally made a vegan potato salad - which I didn't even realize until someone asked what was in it, and it dawned on me that yes, it was indeed a vegan potato salad :P
The full recipe is on Foodista:
Vegan German Potato Salad