A few people remarked at how many games I have accumulated and that it would cost me considerably large amounts of money, quiet the contrary, collecting games isn't as cost taxing as you would think. As you may have noticed I did accumulate a large variety of games, simply because I play all genres, this allows me great freedom in collecting but if you only like a certain genre I don't imagine it is as taxing.
Anyways General Principles!
1.Know your genre inside and out, recognize the lead developers of the genre as well as the up and coming one. Just being able to walk into a gamestore and being able to trust upon a developer regardless of game makes the decision way easier
2. Don't always buy games at launch. Recognize the ones that will run out and are on a limited print, for example, the Zone of the Enders series, 3D Dot Game Heroes, most games produced by Atlus. Games by large publishers will never run out and are almost always overstocked, just hold up, don't buy it at launch, pick it up for half price 2 months later.
3. Sales!!!!!!, recognize game sales periods, I live in New Zealand, for us, EB Games always has a Mid June-Early July stock take sale, Mighty Ape (my favourite online retailer), has a sale every public holiday and daily deals. Also often, because they cater to the import market, you can also pick up discounted unpopular niche titles like Muramasa and Fragile Dreams, two most excellent Wii titles
4. Get into the habit of searching a few key words through ebay/trademe, you never know when someone will drop an extremely rare title with little knowledge for its actual worth
5. Finally, have a list, a list you can either write down or save in your head, have how much you are willing to pay for it and rate them on how much you want them, it gives you such a greater sense of fulfilment especially when you are starting and when you put all your games together and it doesn't feel as impressive