You should stay on the same page and continuously refresh the page - don't get carried away, and I usually start my hunt when I'm sure I'm free the whole day.
Are you looking in the proper area? I was silly and didn't look in the right place the first 30 minutes but then I realized my mistake *blush* Total newbie lol
Here's something that helps me a TON. Turn off images loading automatically on your browser. If you have Firefox, for me it's in Tools > Options > (Content) > Load Images Automatically (which is a little check box). Even on my crappy school network, I'm typically able to refresh every ~1.5 seconds. I've had a lot of success in this manner. You should definitely give it a try. Really, because it's a random number generator-type-thing, the best luck you'll have is if you just refresh a LOT. They have a less than one in one hundred chance (0.8%, or eight in every thousand) of appearing, so you really just want to try and get all those thousands of pageloads.
I don't know if this effects Res getting the hits for their ads, though. I try to let images load every once in a while, just to make sure they get those hits, since they're really very important to keeping this site up and running.