46P Wirtanen
Closest to Sun   2018 Dec 12 at 1.05AU
Closest to Earth 2018 Dec 17 at 0.0776AU
Maximum Magnitude 3.5 in late Dec 2018
Period 5.4 years

Above. Rendezvous of comet 46p Wirtanen with the Pleiades star cluster in Taurus on 2018 December 16.

Discovered in 1948, Periodic comet 46P Wirtanen had an exceptional apparition in 2018 as it passed a mere 11.6 million kms from Earth on 2018 December 17.
From dark, country sky locations, the comet appeared visible to the naked eye as a 3rd magnitude circular fuzzball with a coma diameter over 1 degree.
For comparison, the Small Magellanic Cloud located in the southern hemisphere has a total integrated magnitude of 2.8 and diameter of 3 degrees.
The Andromeda galaxy in the northern hemisphere has a total integrated magnitude of 4.3 and diameter of 3 degrees.
 
The ion tail appeared foreshortened as it points away from the Earth, so a long tail was not expected, maybe a couple of degrees long.
It was directed north-easterly during early December, swinging easterly mid December, through to southerly from late December.

There was a possibility of observing a dust tail or trail around December 14 when the Earth crossed the orbital plane of the comet and we see the enhanced dust tail edge-on.
(update Dec 17 - a faint antitail has been photographed in deep images)
 
Also of note is that the comet crosses the Earth's orbital plane at the same time. This may result in enhanced meteor activity from the Piscid meteor shower.
The comet will cross the orbital plane of the Earth around December 15.
This puts any potential meteors into a focal point. The radiant will be situated in or near Pisces.
However, the comet hasn't been in this orbit for long. An encounter with Jupiter in 1984 reduced the perihelion distance from 1.25AU to its current 1.05AU
(6 apparitions at this distance) so there may not be much dust spread out in its orbit.
The comet appears dust poor, the nucleus is small and dust production appears quite low.
Anyway, it's worth a look.
The encounter velocity would be very slow. Geminid meteor shower peaks at the same time, but should be distinguishable from the Piscids, which will
appear in the early evening.
(update Dec 17 - IMO 2019 meteor shower calendar has prediction according to model calculations by Mikhail Maslov,
the trail of meteoroids ejected from comet 46P/Wirtanen in 1974 passes the Earth at 0.00048 au distance on January 4, 18h26m UT

Light curve data from current and past apparitions can be found at Seiichi Yoshida's website:

http://www.aerith.net/comet/catalog/0046P/index.html

It has shown evidence of an outburst after its perihelion passage in 2002. Hopefully it has a surprise in store for us this time around.

Below is an ephemeris over the observing period at 00UT. (Naked eye visibility in bold)
RA = Right Ascension. Dec = Declination. r = distance to Sun (AU), delta = distance to Earth (AU),
mag = estimated comet magnitude, Elong = elongation from Sun, Phase = ion tail angle Con= Constellation

Predicted coma diameters are based on Guide 9 software using an equation published at: www.projectpluto.com/update7b.htm#comet_tail
For comparison, my observed visual coma diameter on October 20 was 15', thus we can expect 1.5-2 degrees at closest approach.

P/Wirtanen (46P)
Date        RA        Dec         r      delta  mag  Coma Elong Phase Con
1  Sep 2018 01h32m07s -18 13' 16" 1.6681 0.7810 14.0   3' 137.0 24.4  Cetus
11 Sep 2018 01h41m10s -20 32' 22" 1.5831 0.6667 13.0   4' 141.3 23.4  Cetus
21 Sep 2018 01h48m26s -23 15' 35" 1.4993 0.5663 12.0   5' 143.9 23.2  Cetus
1  Oct 2018 01h53m42s -26 12' 58" 1.4178 0.4793 11.0   7' 144.1 24.4  Fornax
11 Oct 2018 01h56m51s -29 07' 30" 1.3398 0.4041 10.0   9' 141.9 27.4  Fornax
21 Oct 2018 01h58m23s -31 32' 50" 1.2668 0.3386 9.0   12' 137.7 31.9  Fornax
31 Oct 2018 01h59m37s -32 57' 35" 1.2009 0.2799 8.0   16' 132.9 37.3  Fornax
10 Nov 2018 02h02m38s -32 41' 06" 1.1445 0.2255 7.0   22' 128.5 42.6  Fornax
20 Nov 2018 02h11m03s -29 35' 26" 1.0999 0.1736 6.0   30' 126.3 46.3  Fornax
30 Nov 2018 02h30m35s -21 07' 35" 1.0698 0.1250 5.0   45' 129.3 45.5  Cetus
10 Dec 2018 03h11m59s -00 35' 48" 1.0561 0.0869 4.0   70' 143.7 33.6  Cetus
20 Dec 2018 04h35m35s +34 34' 39" 1.0597 0.0803 3.5   80' 160.3 18.3  Perseus
30 Dec 2018 06h39m44s +55 39' 47" 1.0804 0.1131 4.0   55' 147.5 29.3  Lynx
9  Jan 2019 08h15m29s +59 31' 18" 1.1167 0.1647 5.0   35' 141.3 33.4  Lynx
19 Jan 2019 09h01m53s +58 16' 00" 1.1665 0.2249 6.5   25' 140.7 32.3  UMajor
29 Jan 2019 09h21m26s +55 46' 28" 1.2271 0.2917 7.5   15' 141.7 29.8  UMajor
8  Feb 2019 09h29m29s +52 47' 40" 1.2962 0.3665 9.0   12' 142.4 27.6  UMajor
18 Feb 2019 09h33m47s +49 31' 46" 1.3714 0.4510 10.0   9' 141.9 26.4  UMajor
28 Feb 2019 09h37m48s +46 08' 25" 1.4511 0.5467 11.0   7' 139.7 26.2  UMajor
10 Mar 2019 09h42m53s +42 44' 34" 1.5336 0.6548 12.0   5' 136.1 26.7  UMajor
20 Mar 2019 09h49m32s +39 25' 26" 1.6180 0.7758 13.0   3' 131.6 27.4  LMinor

As can be seen from the above ephemeris, the comet will initially favour viewers in the southern hemisphere, then switching to the northern hemisphere post perihelion.
The comet's light curve is slightly asymmetric, suggesting a peak 12 days post perihelion.
Northerners will spot the comet from the beginning of December as it rises over the North Eastern horizon after sunset.
Southerners will lose the comet from late December as it dips below the North Western evening horizon.

October 2018
As October begins you will find the 11th magnitude comet situated in Fornax, rising in the East after sunset, and transiting overhead at around 1am.
It treks slowly southwards during the month, near the vicinity of Pi and Nu Fornacis.
Moonlight interferes with evening viewing from Oct 11 but the comet is observable all night (best in the morning sky until Oct 20)
From Oct 26, the comet is now conveniently seen in the evening sky and bordering on binocular visibility at 8th magnitude.
It reaches its greatest southerly declination of -33 on Nov 3 before it starts its trek northwards.