I have been told (I had to cut off a wilted branch and asked the same question) when taking a lower branch, to leave about a quarter inch. The plant will heal and the stalk will not be as prone to attack from the elements. I would also make the cut up and down, as in a right angle to the ground. That way, if it rains.....outside.....the wet will not get into the cut stalk.
Good luck to you.