The most important requirements for any successful comet viewing is a completely dark, clear, unobstructed horizon. Darkness is absolutely essential if you plan to get a good view of the tail.
On 11 November the Comet ISON will cross the orbit of Venus, and by 20 November it will be so close to the Sun that it will be almost sunrise before its head clears the horizon, so viewing it at all at this time might be challenging, demanding crystal-clear skies. By the end of the month, it should be easily seen in the eastern sky before dawn and we might just see the tail sticking up from beyond the horizon before the Sun comes up.
Comet ISON will put on its best display throughout November and December and its coma will look like a tiny ball of light set within a milky glow. From the solid part of the comet, the tiny icy nucleus is hidden within the coma, the tail (or tails!) will arc across several degrees of the sky.
Comet ISON is roughly heading towards the centre of our Solar System and it will pass within 1.2 million miles of the Sun's surface on 28th November when it reaches perihelion (the point when it's at its closest to the Sun) before being whipped around to head back roughly in the direction it came.
As ISON makes its outbound journey, it will pass over the northern hemisphere of Earth at a distance of around 40,000,000 miles on 26th December.
If ISON lives up to the hype, you could expect to see the Comet with the unaided eye anywhere between the middle of November until the middle of January 2014.