Don't forget this bit:
What can be auctioned?
Do some research before creating an auction. Several items have fixed prices in the market. Unless you're offering very rare items, or items with very good rolls, it is better to simply place your item in your regular trade topics and not bother creating an auction. If you have an item but don't know if it's good, you can ask in the forum shoutbox for some advice, otherwise you will look like a fool trying to profit from mediocre items.