If you don't rinse your bike of the salt and crud, immediately after parking it indoors, the best procedure would be to place a coating of wax or oil over the steel frame, keep it outdoors as long as the temperature is below freezing, and there are no security issues.

If your frame is made of aluminum, it won't matter much either way. Aluminum tends not to oxidize to any appreciable rate like steel does.

At the end of the day, all crud and salt should be rinsed off of your bike and the bike placed indoors where it's warm, and can dry, as dissimilar metals in the crud will reduce the rust resistance of the aluminum, but more so with steel.