I'd recommend not changing the contrast from the factory setting. I've found that the contrast is usually set to the optimal setting for the panel and if you mess with it you get crushing toward the black or white end of the spectrum. It becomes really obvious when you attempt to calibrate the display that a lot of stuff is thrown off.
For that reason on my monitor, LG32GK600, I have the contrast on the default setting of 70. I have my brightness set to 30 most of the time, but sometimes if I'm working on a lot of black text on a white background (i.e., word processing) I'll turn the brightness down to 0 just so it's easier on my eyes. Or the reverse if I'm playing a really dark game or movie. But usually 30 is a pretty good medium.
I don't generally have super brightly lit rooms, so I don't need a lot of brightness. I think the display ships with the brightness on max, with it blazing nearly as bright as the sun, so I toned it down a lot.