When I brew a lager, I will bring the carboy downstairs (about 63 or so) and let fermentation start. Once it starts, the carboy is then moved to a waiting fridge that is set around 50. I'll keep it there for about 2 weeks, bring it out at warm for a diacetyl rest for about 3 days, rack, then start to slowly (about 2 degrees/day) cool it to around 28-30, which I will hold it for at least 6 weeks (longer=smoother), depending on the strength. The higher the alcohol, the longer the lagering. I have a 15% lager in now that has been sitting since Sept. 2006 at about 30.