Venus could not be more prominent in the evening sky. It actually reaches its maximum brilliance on December 6, when it shines at magnitude -4.9. By the end of the month, it will have dimmed to magnitude -4.5. The planet is "catching up" to Earth on its inside track orbit. On the 1st, the planet presents a fat crescent disk 37 arc-seconds across and 31% illuminated. By month's end, it will have swelled in size to 59" across, but presents a very narrow crescent disk only 5% lit. This is almost as large a crescent as the planet ever displays. The limit of resolution of the human eye is approximately 1 arc-minute, or 60 arc-seconds. A natural question to ask, then, is whether it is possible to see the crescent of Venus with the naked eye. There are, in fact, numerous reports of people with exceptionally keen eyesight being able to see the planet's phase when it is near its maximum size. The subject is nevertheless controversial. You may want to try it out on your own this month.
Neptune in Aquarius, is the next planet to become visible as darkness falls. As Venus is the brightest of the planets, Neptune is the dimmest - well below naked-eye visibility. In fact, Neptune, at magnitude +7.9, is dimmer than Venus by a factor of 132,000! The planet is large, but now lies at a distance of 2.8 billion miles away; at that distance from the inner Solar System, the sunlight illuminating it is dim, and by the time it reflects off the planet and reaches us, it is very faint indeed.
Another outer planet, Uranus, lies one constellation to the east of Neptune. It is in Pisces, just barely skimming the border with Cetus. Uranus is closer to the Sun than Neptune, so it is brighter by a factor of 7, and actually can be visible to the naked eye under dark sky conditions.
Once Venus has set, it is Jupiter that rules the night. It rises about 7 pm on December 1, and at sunset (around 4:30 pm) on the 31st. The planet lies in Gemini, about 10° from that constellation's brightest stars: Castor and Pollux. On December 10, it passes only 15' - just a half-moon diameter - from Delta Geminorum. As seen in a telescope, the planet swells from 45" to 47" across, and displays a wealth of detail on its cloud tops. The easiest features to see on the planet are two dark belts on either side of the planet's equator. More patient observing will reveal more subtle dark belts and white zones all the way down to the limit of resolution. Besides Jupiter's disk, any telescope will reveal the four large moons of Jupiter: Io, Europa, Ganymede, and Callisto. These are constantly changing positions, and sometimes pass across the planet's disk, or disappear behind Jupiter. Even easier to see are the so-called shadow transits, where the dark dots caused by the moons' shadows cross across the planet's disk. Check the Sky and Telescope website for Red Spot visibility or Galilean moon positions.
Mars has been rather AWOL for many months as far as observers are concerned. That is slowly starting to change. The Red Planet rises around midnight, and brightens from magnitude +1.2 to+0.9 in December. As seen through a telescope, though, it presents a tiny disk just 7" across, too small to show much detail. Take heart, though; the planet's prospects will improve significantly in 2014.
Saturn in Libra, rises about three hours before sunrise. It shines at magnitude +0.6. As seen in a telescope, the magnificent rings are now tilted 21° to our line of sight.
Mercury remains visible in the morning sky the first half of the month. It displays an almost-full disk about 5" in diameter. But it soon disappears from view and reaches superior conjunction with the Sun on December 29.
Pluto is too close to the Sun to be easily visible this month.
The dwarf planet/asteroid 1 Ceres, in Virgo, rises about 2 am local time, and is visible until dawn. It is currently at 8th magnitude.