You have to use the auction house to make money. Trade chat is simply not time efficient, unless your money making strategy is (a) winning rolls on BoE epics, or (b) selling cutting edge craftables the second they become available. These strategies are not options for the average player.
Here are some basics dos and donts for the AH:
Include a buyout price! Most WoW players are driven by a desire for instant gratification. If you don’t supply a buyout price so that they can get their hands on the item right here, right now – you have alienated most of your potential buyers.
Know the value of items. The more you familiarize yourself with AH and the pricing of high volume / needed items, the more able you will be to spot the opportunities.
Day of the week. Demand is highest on weekends, when the most people are playing (Friday evening through Sunday evening). After that, evenings (especially Tuesday, since servers are reset early on Tuesdays) are next. Unusual items are more likely to bring better prices at busy times.