Much like an encounter with a wild pet team, PVP Pet Battles are turn-based. However, unlike the PVE version, the PVP combat system is timed and any ability for each round must be chosen within that time limit otherwise it will assume you have passed a turn. A time penalty is applied if you take more than 15 seconds to choose an action, resulting in progressively shorter round timers for you.
The most simple thing is TradeSkillMaster. This AddOn shows you quite an amount of information in the items tooltip. In my opinion, DBRegionMarketAvg the best source. It tells me the price, an item was posted on all EU realms in the last 14 days. Why not DBMarket? DBMarket only shows you the items value from your server in the last 14 days. This value often gets manipulated. Some people start to post an item with a 500g value for 500.000 Gold on the auction house for several weaks. As a consequence, DBMarket is rising towards 500.000 Gold.  If you use DBMarket with 100% and post your item for 500.000 Gold, nobody will buy it.
The old popular example was the This item differed on my server from a high of 6k to a low of about 3k. When the price was down at 3k, I would buy a few of these and just wait a week. Throughout the week, I would put in trade and the auction house that I wanted 6k for it. I would then immediately go onto an alt and say that I only wanted 5200g. Sometimes, I would get the 5200g and be a very happy man, other times it would take more patience. However, almost always, by the end of the week, the other sellers had reposted for around what I wanted. This gave me a huge advantage. Now, the price ceiling was no longer 3k on the auction house, but 5k. I could now easily sell the few I bought for 4 or 4.5k, which is a huge 50% profit from the 3k I originally invested.
You will need to cover very large areas in order to get a few chests as they are quite rare. Vanilla, TBC and WotLK zones work best. The way I like to do it is to park one Rogue class trial in Outland and one in Northrend, then fly over the whole continent and look for chests. One whole run might only yield 3-10 chests but you will still make a bunch of gold as you are almost guaranteed rares in chests in these zones.

This farm almost did not make this list. Even though I have had only a little luck with it, it seems to be gathering some popularity in the gold farming community.  Although I feel with the recent changes in 7.3,  this farm is very close to dying out.  Generally what you want to to do is pull every mob you can as you venture to the last boss in the instance.  The only saving grace of this farm (if you can call it that) is that some mobs are GUARANTEED to drop greens.  Guaranteed.  Whether or not they drop profitable greens is a different question, however it's a must-mention quirk you get from running this instance.  It also allows you to get your hands on some rare low level blues.