I'm with Ray and John. I just take it out, go through the menus and turn on any options I know I'll want, then go shoot it. If I get stumped I'll google something (I've never read a camera manual, except for some parts of the Nikon D600 manual because I didn't know how some of the features worked). After taking some images, I'll run them through LightRoom and look at the sharpness/IQ and how they respond to my usual post-processing workflow.
From there just like Ray said, I either start bonding with the camera, or not. Usually that's my indicator whether it'll stick around or not. So far the only exception was the Sony RX1 - it took me a lot longer to bond with, but now I love it and would really hate to part with it.