I try to find particular games, but I don't just wait till I get find those to get new stuff.
I simply look around, and if I find something I like, I get it. If one the items I want is listed, then cool!
Proud owner of a Neo 25 Neo Geo Candy Cab!
my collecting was kind of random at first. i started back in 2000 when i went to Funcoland for the first time and saw tons of snes games that i hadn't seen since i was 14. so i started going there almost weekly and buying all of the snes games that i wanted as a child for cheap. as a result i now own around 120 snes titles but i collected about 90 of those titles in about a 3 month period just going to Funcoland and blowing my measly YMCA check.
Now i collect for around 15 systems. Most of the classic systems i own now are from the early to mid 90's including the sega cdx/atari jaguar/saturn/3DO
i usually only buy the games i'm actually gonna play for the xbox 360 and the nintendo wii.
currently i'm looking to finish up my fighting game collection for the dreamcast.
anyway, i guess my collecting is still kind of random, but i refuse to pay full price for new games and the most i've ever spent on a classic game was around $40 and i will never do that again.
i generally have like a $20 rule in my head with most games for all systems. thats pretty much my limit and i try to go much cheaper.