Yarn (approximately 1/2 skein per color) Cording/Piping (approximately 9-10 yards) --I used Wright's 6/32" Cotton Filler Cord meant to fill in pillow trims. Scissors Marker(s) Yardstick Ponytail holder x 2
Step 1:  Purchase 9-10 yards of thin piping or cording (about 6/32"  in diameter/size).  Piping--trimming meant to be stitched along the edges of clothing, slipcovers, or curtains--comes as either cotton or polyester, usually in a package or on a spool.  If can often be purchased by the inch or yard.
Step 2: Measure with a yardstick how long you wish your tail to be, and mark that length on your piping with a marker.  DO NOT CUT.
Step 3:  Double the length of the cording and make another marker dot.   For example, if your original length was 30", you will now have 60" of cording. DO NOT CUT.
Step 4:  Add 15" to the length of cording and mark it.  This is to allow room for the tail loop and braiding. For example, if your original length was 30", you will now have 75" inches of cord (30" + 30" + 15" = 75").  NOW MAKE YOUR CUT AT THIS MARK!
Step 5:  Cut two more lengths of cording to match the first.
Step 6:  Bend each equally in half.
Step 7:   This step is optional--to help me keep each cord straight, I ran a marker down two of them.
Step 8: The "U" of each cord will become the loop for the tail belt.   From the very center of the "U" (where the rope turns in half), measure approximately 3.5" inches in either direction and mark with the stopping point with a pen/marker. Starting at one mark and working towards the other, choose one color of yarn and wrap it tightly around the piping.
Step 9:  Now choose your main yarn colors and create strands 7"-9" long by and wrapping it around one hand as shown....
Step 10:  ...and slipping it off my hand.  You now have an oval circle of yarn. Cut the yarn at one end so that the oval forms a 'U'.  Voila!
Step 11: Bend your cord in half as follows, and begin tying yarn onto it (see step 12).  If you want to do stripes instead of a general blend of colors, keep the yarn colors similar on both sides. When you are finished, this doubled-up length of cording will be the first of the three "ropes" required to make a braid.
Step 12:  Take one to two strands and knot them around the cord, starting at the bottom.  I have found that using more than two strands at a time is counter-productive.   Spacing is very important.  Unlike traditional yarn tails, when making a German tail that the goal is not to make each length of piping thick with yarn; instead, you simply want to wrap each piece of yarn about 1cm apart. Any closer and your tail will become extremely thick and heavy when braided.
Step 13:  Repeat until your entire cord is finished.
Step 14:  At this point, I add in a few strands of specialty yarns/embroidery threads/pieces of fabric (which authentic German tails have) here and there to create a more varied look.
Step 15:  Repeat steps 8 through 14 for your remaining two cords.
Step 16:  Line up the tails so that they bend in half with the middle of the wrapped area forming a "U" over two fingers fingers.  Slip a ponytail holder or rubber band around all three and pinch below your fingers.
Step 17: Secure all three together with a ponytail holder, and tie a piece of yarn at the very top of the "U" to hold all three together.
Step 18:  So now you have six strands coming out from your tail belt loop, right?  Match each one to its "partner" (this is where the marker color-coding comes in handy!)  and separate them so that you have three sections. This may seem tricky, but it's really a piece of cake--I'm just going through it one tiny step at a time.
Step 19: Begin braiding and continue until you have about 1.5" left.
Step 20:  Wrap a ponytail holder tightly around the base of the braid, pulling yarn out of the way as you go.
Step 21: Pull the yarn over and you'll never know it was there!
Step 22: Slide your finger or tool (I used a mail opener as a substitute so I could photograph) beneath a "pocket" of yarn that has been "trapped" in the braid.
Step 23: Gently use your finger or tool to loosen the yarn until it slides out from the braid.  Continue this on various sections of the tail until it has achieved the fullness you want.  However, you may want to consider leaving some of the yarn trapped in the braid; authentic German tails are a combination of loose and trapped yarn, which makes them so unique.  I decided to pull out most of my yarn, but on future tails, I will not loosen quite as much.
When working with yarn, start at the bottom of the tail and work your way up.  This way the yarn will lay correctly. For a spiky Macavity tail, lay the yarn as a 'V' rather than an inverted 'V'.  (Still start from the bottom). Blended yarn will create a more authentic-looking tail than solid blocks of color. Wear rubber gloves and safety goggles when working with superglue (my favorite brand is "Surehold Plastic Surgery" found at ACE Hardware).  Superglue actually releases visible fumes that can severely irritate the eyes (I was once unfortunate  enough to have this happen to me).  If your fingers or skin become accidentally stuck despite your precautionary measures, a product called "Unglue" or "Uncure" found at local Hobby Shops will help unstick your skin. I always have a bottle  on hand when working on projects that require superglue.