man_in_poland - 12:21 pm on May 5, 2008 (gmt 0)
Option 4) sounds troublesome, IMHO. In theory, it could be good, but having some pages on one domain and the others on another sounds like an accident waiting to happen. If you do move the least important pages, you'd still have them linking to the more important pages on the original domain. You'd have to be VERY accurate with this sort of approach. I understand your concerns, having done this myself - but the very best thing you can do is to do it in one go, and PLAN, PLAN, PLAN before you make the switch. Take your time before the changeover, but when you flip the switch, do it as fast as possible, checking IMMEDIATELY thereafter with a server headers checker to make sure all old urls are pointing correctly to the new urls and sending the correct server header. Good luck!