Looking at the search hits, it seems like there are many people still struggling to figure out the warhammer auction house and how to best utilize it. I'll try to give you a quick rundown...
The most important thing to notice: When you hit the search button on the auction house (AH), your chat window will give you a number of results. If it states search results 500, some auctions have been cut off. The AH will only show a max. of 500 results at any time to you. Should you hit this magical number, its adviced to refine your search more to see all fitting auctions. Some features on the AH are still a bit bugged, like search for career related stuff, you'll always get some crap you can't use as its for someone else. You can sort results by clicking on the column top like name, rank, time left, etc.
From my use of the AH, your best tools are these (until the rest gets fixed):
# Item Name - enter a search keyword in here and you'll only get results that include it, use this!
# Rank from x to y - if you search for gear to buy, limit the search by a rank frame that makes sense. With rank 20 you don't want to search for rank 1 gear.
# Categories - if you only search for armor, weapons or crafting stuff you should use this one.
What about selling stuff at the auction house you ask? Well, the warhammer auction house UI makes it really simple for you. It tells you the the vendor price (good stuff!) and suggests a price connected to the vendor one with a little markup. Careful tho, some crafting material does not sell for much at the vendor, so its worth more then the AH suggests. If you think that the drop you found is only mediocre, you might want to take the suggestion (pending on the drop up it a little). I'm still amazed how many players try to sell crap rank 17 items for a few gold, no one will buy that stuff. If you have no idea how much its worth, use your common sense (would you buy an item for 5g at rank 17?) and search for the item first to get an idea about how others priced it (which does still not mean it's worth 4.9g if you know what i mean). You might want to adjust the duration tho, the default 24h seem a bit short. As a last sidenote: Your mailbox has a seperate tab for mails from the auction house - how could you miss that? ;)