I'm not sure if I understand the question, but:
Buying low, selling high. I know a few people who just watch the market the whole time they're on.
When they see someone desperate to sell something pricing it low; they buy it, and either resell, or
unslot and resell. It takes a lot of patience, but they make quite a bit of money off it.
If it's a question on how to make money, Niff'ing usually isn't the first thing you'll do; as it requires an investment.
Farming Blue herbs in the YGG tree, or Ganking' cake from Toyfactory 2 on a rogue are two good ways of starting out.