Okay, speaking of pet farms this one is a really unique farm.  What we're looking for is the carrier cage : black tabby.  This is a very sought after pet for both horde and alliance – which is why its price competitively at 55,000g.  The farm takes place in Hillsbrad Foothills on a peninsula like piece of land just northwest of the yeti caves.  There will be dozens of stormpike engineers surrounding ballistas that only horde characters can kill.  However, that doesn't mean alliance polayers can't do this farm (im alliance myself).  All you need to do is to create a class trial (monk is the best) and send him over to the grinding spot.  Use the black ox statue to attract the mobs, and easily maul them down group by group.  If luck is on your side, you can make out with an awesome black tabby carrier.
Making gold is all about finding the balance that works best on your server between all the above methods. When you find that balance, repeat, repeat, repeat, until you get the results you want. Never make any rash decisions without first consulting the economy. If you do not think you can make a for sure profit, then do not do it! Change only when necessary, because your clients become accustomed to certain practices that keep them buying from you even if under cutters offer a slightly lower price. If the customer is always right, then show that to them and you will be much more profitable!
Only really to expand on Gráinne's comment as regards the 'collecting' and 'roster development' sections - which are, as said 'distinct' although they are intrinsically linked - I would like to point you in the direction of the in-game Achievements > Battle Pets > Collect tab. There are a series of achievements called Raiding With Leashes, pretty much all of which can be completed via the auction house - if you have the gold/inclination - or by completing old raids.