Space Station Part Operation

[Dragon2711]

The part is a gyroscope, like the ISS has. Keep the station plane level with the ground at all time. Not SAS, which lock out rotation to where you engage the system.

[shadowfax]

Mechjeb will do this as long as you stay within physics range of the station. Just set it to point toward surface velocity + and control it from a part that will face forward when the station is oriented the way you want it. Once you go outside of physics range, the station will be put "on rails" and won't change anything about its orbit or orientation until you get back in range, at which point physics restarts for it and it will re-orient itself.

Where you can get in trouble with this is if your station's rotational capabilities are fairly powerful and you don't have it braced well enough - it'll start flopping around like an electrocuted octopus and might blow things up or tear itself completely apart. When I do this trick, I always attach a bunch of struts to the station first (Kerbal Attachment System lets you do it on EVA) to be sure it's braced really well and can't flail around.

[Starwhip]

With the new vector holders in the next update, this is going to be trivial. Just set to "Radial In" and presto!

EDIT:

With a "downward" facing part, of course!