As well as pulling up runners and replanting I take lower woody cuttings from when you cut down at end of season.
I plant about 4 cuttings in deep pots (those supermarket type flower ones). Find that at least one or maybe two of the four will root and can then be planted out the next Spring.
They tend to have long trailing roots in the pot, so you know they are running healthy. The ones that just do not not want to grow die after a month, so do pull them out the pot.
I take a cutting about four to six inches that has some nodes present and dip it in some cinnamon (or rooting powder( before placing them around the edge of the pot.
Just leave them outside and unless its dry over the winter, there is enough water to keep it going.