I personally use the old flower picking method. All of my characters have the same professions, herbalism and alchemy (I am an exciting guy), and when I am short on cash, I sell some flowers. I usually do my rounds in some of the herb-dense zones early in the morning, and I sell a few stacks in the evening. It is typically good for anywhere from 25g to 75g depending on the server or the day of the week. Saturday is a great day to sell, Tuesdays...not so much.
What is your secret? How do you earn cash when you need repairs or some sweet new crafted armor?