1: Try Trade chat as a first resort. No auction house listing fee or cut. You can markup your items less and still make make more profit vs the Auction House if you find a buyer directly.
2: Check how much competition you have before you list your auctions. There might be someone who didn't notice the 10% cut that's selling the items at a loss (or is sick of holding onto the item and is trying to "clearance" it). You won't be able to sell your item until that person's auction ends.
3: For starting bids higher than 2,000 Crowns, there's little to no benefit in setting up an auction for anything less than the maximum duration.
4: When you'd otherwise be just idly hanging about Haven (Spinning Around Haven is the new Jumping Around Orgrimmar!), you can advertise the items you have on the AH in Trade chat again.
5: You can try buy-low/sell-high, but this is simpler on the Energy Market due to the ability to make offers on both sides of the equation and the lower cut.

Yes, OP.

There's a message in-game where it says: "only sell your shinies at AH" or something. Since there's a list fee, there's a risk of losing money if you don't sell the item. So, only sell your best items, the popular stuff.

There are only four 5* recipes that you have to sell at a loss (or as an alternative to paying your fine, you can serve out your sentence in trade chat... ),
Justifier set and Skolver set.

On the other hand, there are probably only four 4* recipes that sell at a profit - Ashtail set, Avenger, Faust. Maybe, if they didn't go down in price overnight. You have to be very picky about which 4* recipes you get and I've more or less given up on them.

As more and more people discover the auction house, the market is starting to stabilize - some mats are showing a steady upward trend in price and some a steady downward trend as more and more people get into auctioning. (Having price trends is stabilizing compared to prices wildly jumping around every few hours, but not stable, of course.) Recipes are very different though... even mass crafters only need one. And anyone with crowns is a potential recipe seller... sooner or later supply will outstrip demand and all recipes will sell at or near cost.

Buckhaawk its works basically this way. Listing price fee is 10% of whatever the listing prices is - so if you put up a recipe for 25k crowns and have a buyout of 50k crowns. The AH charges you 2500 crowns to place that auction up. Then upon sale - lets say it goes for the full 50k buyout you get your listing fee back. However they take a 10% sales fee out of the total selling price of your item.

So 50k + 2500 = 52,500 - 5000 (10%) = 47,500 so you make 47500 overall, not bad, but obviously not the full 50k.

This is worse if say you don't sell, they take the Listing fee so if you don't sell the first time you are out 2.5k.

Basically you want to put up stuff you know will sell the first time, and at a decent price. so you can make a bit of a profit. The AH taking 10% is a bit harsh if you ask me. Especially off the selling price.