Well, we would need a little bit more of a specific idea of what you’re talking about. I’m assuming you mean primarily indoor photography? Could you share what camera you plan on using? It could make a big difference whether it’s a DSLR or a P&S (point-and-shoot) camera.
Sharp pictures start with having the focus correct. Lighting tends to be really bad indoors, and auto-focus systems don’t usually do too well in low-light, so it’s imperative to check your pictures and make sure that you’re getting them in focus. Something to remember is that auto-focus works by detecting contrast, so always try to put your auto-focus point over an area with contrast. Maybe a black tie on a white shirt, or maybe just the contrast of dark eyes on a light face. An easy way to confuse the auto-focus sensor is to point the camera at something that is all the same color, with no contrast. The sensor has no way of knowing if the camera is properly focused or not, especially in low-light situations, so try to remember to keep your focus point over an area with some good contrast. If you have to, you can focus, then recompose to get the composition that you want.
Another factor in “blurry” holiday pictures is motion blur, which is also related to the general poor lighting conditions indoors. Keep your aperture low, and increase your ISO till you have a reasonable shutter speed. If there’s lot’s of action you’ll need at least 1/100 shutter speed, if not more! Set your camera mode to ‘Aperture Priority’ and select the lowest aperture possible, then experiment with the ISO speed till you get a proper shutter speed. Again, keep an eye on your pictures as you take them, if you see motion blur, crank up the ISO a stop or two! It’s much better to have a grainy picture than a blurry one. (That’s just my opinion, of course…)
Another option of course is to use flash. I generally try to avoid using the on-board flash, as it creates quite harsh “straight-on” lighting, and the fall-off tends to create a very dark/black background. Ideally, you’d have a house with white ceilings, and you’d bounce a slave flash off of the ceiling (or even the wall) for softer indirect lighting.