We've been making this stuff ever since we moved to Seattle, as blackberries are a weed and a nuisance. But at least they can be useful, unlike other invasive species.
Stage 1 - acquire the ingredients:
4 pints of blackberries
6 cups sugar
4 cups 100 proof vodka
Mash the berries and put then in a 1-gallon glass jar, then add the sugar:
Measure out and add 4 cups of cheap 100 proof vodka. Really, seriously, use cheap vodka.
Then you stir it:
You want to make sure to stir it before the next stage, adding water to the top of the jar, because it can get a bit messy trying to mix up all that sugar in a full container. It takes about 4 cups water to fill it to the curve at the top of the jar:
Now I'll cover it and stick it in the bottom back of the pantry and forget about it for 4-6 weeks, then we'll strain it and bottle it, and let it age till next fall. Time to start saving up the wine bottles for re-filling.