Now, I've only made about 5 batches so far, but i strictly follow this recipe each time and it always comes out great:
Get 4 lbs of whatever meat is on sale.
Get 1 lb of pork belly to add some extra fat
Add in a cup and a half of leftovers from dinner last night
Season with one tablespoon of fennel, a tablespoon of salt a small head of garlic, and a tablespoon of whatever spice blend you grab out of your spice cabinet (actual measuring optional)
Mix all that together stuff into casings.
Bake to cook
Eat on a roll with mustard and kraut, because otherwise you are an uncivilized heathen.