Are you talking about getting new plants from an established patch? If so, they send up shoots like suckers. They are just attached at the roots. Just dig and use your clippers to cut/detach the plant, taking part of the root. Normally about 4 or 5 inches or so.
They are probably one of the easiest plants to get starts from. Good luck. One more thing, next spring after they are established, get some rabbit manure and put on them. That is one of the best fertilizers since it doesn't burn. You don't have to let it age.
I used it on my raspberries one year and then put several inches of sawdust on top of it. I had the best and most berries that year than I had ever gotten.