How to get money:
List your favourite ways of earning money in WoW
Here's what I did, it worked fairly well.
From level 1-50 I mostly bought things in the auction house and resold for more. On my server this worked well with wool, silk and linen.Every once in a while you might find an epic or rare item which you can buy below it's average prize (check thottbot and allakhazam for those).
From level 50-60 I got most of my money from Large Rope Nets which drop from Devias trappers in Westfall and selling discombobulator-rays(engineering-item). Of course this works best on pvp-servers.
From level 40 on you can farm turtles, with a bit of luck you will find golden pearls which sell for at least 20G a piece. If you can skin those turtles and sell their leather and scales it's even better.