Ok, so we've discussed a number of different angles for finding abandonments. You'll recall that I mentioned driving around, and I mentioned several times using Google Earth as a research tool.
So where are you going to have the best chance of bumping into something? How do you narrow down your first searches if the idea of research doesn't really get your blood flowing?
When looking over the satellite photos of a given town or city, I find it useful to first locate the industrial area(s). Clearly, with manufacturing moving out of the country, it tends to leave many an empty shell behind waiting to be explored.
Generally speaking, the largest number of industrial areas tend to be close to water. So spend some time following various waterways on Google Earth. Sometimes you get lucky and discover something interesting.
Another good place to look is along railways. Almost every town has at least one running through it. Find a railway and follow it. You can often see grass growing through the pavement in parking lots and that tends to be a good clue it hasn't been used in some time. Another great giveaway is the condition of a building's roof. Many abandonments I've been to have some pretty large holes in the roof and those will show up quite nicely in Google Earth images.
Look also for places where the property seems unkempt. Maybe you notice the front lawn looks from space as though it hasn't been mowed in several months. Perhaps the road leading to a group of buildings doesn't show as much wear as it should, or is becoming overgrown. There are countless clues that might lead you to something interesting and are all great places to start.