It's clean-up time around here. Now that the WoW Rookie Guide is up and running to shuttle you to precisely the information you've been wondering about, we're poking through our older pieces to bring them up to date. (If there are any WoW Rookies whose datedness you find especially galling, shoot me a link at lisa [at] wow [dot] com and I'll prioritize it for updating.) Sometimes during the updating process, I uncover little gems, like this excerpt from Elizabeth Harper's 2007 piece Money-making 101. Be sure to visit the entire article, by the way; it's an outstanding resource to make sure you arrive at your character's more costly milestones with gold in your pockets.
In the meantime, let's talk about what's worth selling and what's not. First of all: keep everything. Make buying or making big bags a priority; after all, you can't make money if you can't bring home loot to sell. If your bags get full, sure, go ahead and destroy grey items (items with their names listed in grey letters). (To destroy an item, left-click it, drag it to an open spot on your screen, and left-click again to drop it; reply "Yes" to the dialog box that pops up.)