+ bing, streets and trips, plain google, local post office and Po Po, Netronline/Assessors office. If two or three of those don't work, it gets bumped back to the client. That is their homework to begin with.
I generally use google maps if my GPS doesn't find it, but about 1% of the time google maps is dead wrong. So if I get there and it doesn't exist or I am suspicious of it I will cross check with mapquest
I had one a couple years ago that was 5 miles and on the other side of town from where google earth and mapquest said it was. When I drove up the driveway the guy said that preservation people had been coming by his place for like 2 years looking for that address. I ended up stopping a sheriff and asking him, he had to call his dispatch and then he drove me over there.