Earning gold is one of my favourite things to do in MMOs. It doesn't seem to be that easy in Guild Wars 2, however, compared with a few other games I've played. With the abundance of armour and weapons dropping, hardly any of them are worth more than 1 copper above the merchant price. But if you want to earn gold in the game, make sure to not sell items for just one copper above merchant price!
It is a great blog post about Guild Wars 2 Coins !