I'm a simple person. I don't bother with having a lot of gold on my character, nor do I have any intention of hitting the goldcap. I probably could do it easily, if I just went for it, but I've never really had any incentive to actually do it.
At the time being, I'm just below 10,000 gold and happy with that amount. I simply do not need any more than that. It covers repairbills, potions and is enough to buy some upgrades from our GDKP raids. (Not that there's been an abundance of useful stuff dropping in ICC when I've been tagging along, but that will come.)
Also, it is enough to replace one of my professions, should I chose to do so.
My rule of thumb is that if I drop below 5000 gold, I'll start playing on the AH and usually stop bothering getting more when I reach 8000-9000 gold.
The way I do it is easy, as I craft only one thing to sell; the Eternal Belt Buckle. It's an item that people have need of fairly often, as many replace their gear on their main characters or on their alts they are gearing up.
As it is with the prices on Agamaggan now, you can sell the belt buckles for anything from 55g to 30 gold. Sure, you get the occasional "I farmed it, so it's free"-poster that sells them for way less, but those are few and far between.
Seeing as the costs for the mats are about 27 gold in total, my limit is set at 30 gold as the minimum price I'm willing to sell for. Below that and I consider it a waste of time and money, as I can rather go do some dailies.
So this week, I've gone from about 6000 gold to around 9500 gold. Take out about 750 gold income from the GDKP-raids, I'd say it's not too bad a result for selling only one thing.