It's much easier to get sales if you sell smart. Too many people put up items in huge quantities. If its a fairly common and unused item, sell in small sets. Armorsmith, i generally don't need 50 HQ Aldgoat leather. I need 2-5 at any given time. Iron rivets HQ are up on my server for 1500 per item but in large stacks. 10-20. I put mine up for 2500 in sets of 1 or 2. All were sold over night. People don't want to buy mass quantities all the time, look at the items use, commonly sold amounts before sticking anything up there. Obviously there are exceptions like Ores and such.

If someone under cuts me by alot, and I've seen this quite often and at stupid prices at that. Items below NPC value. Buy that crap up if there isn't a massive amount, resell it. Even if there is a massive amount of items for sale lower than you. Buy the cheapest ones, less competition, adjust how large of stacks you are selling. Make it appealing to what the crafters need number wise.

And if all else fails. Wait. Patience pays off more often than not, it can be extremely frustrating. I had sat on items for weeks at a time before they sold but they always sold and often without touching my initial price. The market is a game of patience, people who lack that will lose money and be taken advantage of.