5. Watch Your Aperture
I quite often shoot in Aperture Priority mode ("Av" on your SLR) on a day like Christmas! I'm generally too busy preparing the hors dourves or wrapping a last minute gift to shoot in manual (to control every aspect of my photo).
So, for example, when taking shots of a champagne flute, I’ll select a large aperture (a small number like f/2.8) to throw the background out of focus. But for a shot taken from the end of the table of everyone sitting down to eat, I’ll choose a small aperture (like f/8 to f/11) to give me a larger depth of field and keep everyone in focus. This gets easy with just a bit of practice, promise!