Your flute will probably sound a bit different after you oil it, but will quickly regain its normal tone. Again, this makes sense intuitively and is unlikely to cause any harm, so give it a try. Patrick recommends oiling a new flute at least once a week. Legend notwithstanding, it is not a good idea to pour Guinness down the bore of your flute or leave it to soak it in a barrel of water. Don't do these things if you value your instrument.
Cracks can occur with sudden temperature changes, as metal and wood expand differentially.
Wrap up your flute if you have to take it into the cold and leave it wrapped for a while at room temperature to warm up if it has been outside for long. A good, padded flute case should help protect your flute from temperature changes and other potential dangers. When you're not playing, it's a good idea to keep your flute broken down and stored in its case, rather than leaving it fully assembled. If you have cork fittings, the cork may lose some of its springiness if it's kept constantly compressed, eventually leading to looseness in your flute's joints. Australian flute-maker Terry's McGee's home page has additional information on flute maintenance.