If you enjoy occasional AH manipulation rather than staking it out all day, here are a couple searches that should help you earn a little money while you are out in the game world having fun.
Of course, you need a functioning and hopefully up to date version of the auctioneer mod. I think I got mine from Curse. Next, you need to have done some scans, or at least look at the items you're in the market for a couple times per day to keep track of trends. Scans don't take very long anymore; esp if you are on a medium to low pop server. Just start the scan and afk or browse the internet, etc. This will update and save current AH prices, averages, deals, etc.
For new users, the benefits of auctioneer are being able to see more items per page, accurate price sorting, tracking averages/means/medians/moving price/last won for/etc. It also displays prices in % relative to average pricing on said item.
There are the items I usually look at when I am just playing the AH casually:
19-49 twink blues
Blue quest items such as bijous and darkmoon cards
uncommon/rare/epic quality recipes
inks/herbs/other trade goods
Simple seach for 19-49 twink items:
-all items (or you can search weapons first then armor, etc)
-set threshold to rare
-level range 2-49
-organize by Buy Total, lowest to highest (lowest on top)
Look for blue %s and missing %s (no % value means your auctioneer hasn't seen the item before and it could be very rare if you check AH daily)
Double check before purchasing item to make sure it's less than server average
I also like to look at the epics.
-set threshold to epic
-no lvl range
-organize by Buy Total, lowest to highest
-manually tab through pages and look for very low prices. Epic armors and weapons require a larger deposit than other items typically, due to their high vendor value. Don't buy something very common at a high price or something you can't flip or you'll be reposting it forever. I mostly look for items like Shadowblade, Blood Razor, Krol Blade, 70 epics from outland world bosses (doomwalker gun for instance), etc. Underworld Bands and such. You can make huge profit from someone else's mistakes.
huge money potential here.
-set AH search to recipes
-set threshold to uncommon
-no lvl range
-organize by Buy Total lowest to highest
Look for super low % in blue and missing %. This is the area where you will see the rarest items the most often. Old world recipes and Outlands recipes can still net you 100s of gold per flip if you get to know what you are doing. Just start familiarizing yourself with prices, what's common and what's not, what people are farming and what people look for in trade chat. And always remember to undercut if someone keeps screwing with you, especially if your target selling price is significantly greater than the cost of the item. Don't get caught in the cycle of holding onto something that you can't use forever just because you can't get the price you want. This wastes precious bank space and is depressing. Of course there are opportunities to really profit from high pricing when you know you've got the only one and people want it.
*Example recipes: Insane Strength Potion, Star Belt, Weapon Chains, mechanical Toad, things like this.
This is a little less convenient as there is a ton of crap listed under trade goods. Just look for low %, you can also switch to Buy Each for this to make sure you're getting the lowest price. Herbs and ores, especially hard to get ones from lower zones (swiftthistle, gold ore, etc) can flip nicely if you can snatch them up. I like to put bids on all the stuff with a super low bid and no buyout. Look for auctions ending soon and put bids on good deals. You'll eventually win something.
I can add to this later. If anyone has questions please pm. I know this is simple but for a novice to auctioneer it's a decent approach.