The comet ISON, or more formally, C/2012 S1, was only discovered in late September last year, but it's already becoming somewhat of a superstar. That's because it's headed for a very spectacular encounter with the Sun, one that promises quite a show later in the year.
Astronomers aren't sure just how visible the comet will be, but at its peak it may be brighter than the full moon, clearly visible in the sky.
The comet is too far away to be visible now, but you should be able to make it out with the naked eye starting in late October this year.
ISON will come very close to the Sun, just 1.8 million kilometers or 1.1 million miles from the Sun on November 28. If it manages to stay in one piece, it will be incredibly bright at that point. It will also be incredibly close to the Sun, making it hard to spot against its glare.
In all likelihood, it will be easier to see in December, again, if it survives its close encounter. These estimates will get better as the comet gets closer to the Sun, but you don't have to rely only on guess work, there's now a tool that tracks ISON's position in the sky, so you'll know where to look for it.