I've got several mats rounds I know of, especially mature herbs and logs. I'm also 400 in leatherworking, so rare materials to globs or just re-selling also make a nice profit. All goes toward some sweet looking Tier 3 Cultural Armor (Sylvari) (the two in the middle). I almost always list the items for the highest price on the Black Lion Trading Post, and it always sells in the end.
How do you make money? Node/mats/item farming, playing the Black Lion Trading Post?
If anyone wants any tips, I'm willing to help. I've developed several routes and routines based on other peoples work combined with my own personal experience. Also check GW2 Riches, a legitimate gold making tips website (the current admin is stepping down atm., but the site will stay up). It's not cheating, it only helps you maximize your income timewise.