There are lots of tutorials out there for making Duct tape dummies or DTDs.... however I still sometimes get DTDs which are poorly made and make it really frustrating to work with.
Some makers will refuse poorly made DTDs, and others will tough through and try to make lemonade out of lumpy-bumpy-falling apart lemons :P

I think the main problem is even with a million DTD making tutorials out there, people assume that maybe they are clever enough or cheap enough or lazy enough to find a better way to make one. However, please note.... makers give you a tutorial for a reason: we work with these all the time. We know how to make a good one.... and we know what makes a BAD one. Perhaps the reason we still get poorly made DTDs is because no one ever explained WHY you shouldn't do certain things.

Let me lift that veil! Here are some ways NOT to make a DTD!

1) Do NOT use pantyhose or spandex or any stretchy material as a base.
-The reason makers suggest painting smocks is the are non-stretchy, made of a thin material that is easy to cut with scissors, and come in an assortment of sizes which can be modded as needed with some paper towel. Stretchy material is HORRIBLE for DTDs because once you are done taping and remove the clothing, the stretchy material will attempt to unstretch back to its original shape. And when it does so, it takes the tape with it, and your entire DTD will pucker in on itself and all of your work will be ruined.

2) Do NOT plant a starting point and simply unroll the tape like you are wrapping up a mummy.
-Duct tape is... well tape. It's sticky! Anyone who has attempted to unroll any length of tape will notice that it somewhat sticks to itself and requires a minor bit of force to pull from the roll. Taping someone up like this means that the additional pressure you add to pull the tape from the roll as you go is making the DTD tighter and tighter and tighter on the person being taped! This makes the DTD making experience uncomfortable and intolerable as the circulation of blood is cut off during this taping torture..... not to mention the added impossiblity to cut said person out since they are wrapped so unbearably tight.

Please cut and use SMALL pieces of tape and place them on the person's body as you go. If you need to you can pre-rip tape pieces or have 2 helpers (a tape ripper and a tape applier), this will speed things along.

3) Do NOT forget to make tick marks along your cutting lines..... and if you use BLACK duct tape, make sure to use a different colored marker that will show like a silver pen.
These lines are used to assist in reassembly. We use these marks to line up the pieces when we put the DTD back together. Although you can put a DTD back together without them - if you have patience and good eyesight to see how the tape lines match up - it speeds the entire reassembly process along exponentially.

4) If using old clothes for the DTD base, do NOT leave your shirt untucked.
I know this sounds weird, but once you've put together a few DTDs you will understand the logic of this.... when stuffing the legs/hip area of a DTD, most people go in through the neck. This means we are taking handfulls of stuffing and pushing them in through the neck to the thighs/hip area. If you do not tuck in the shirt, we may start pulling the pants portion of the DTD away from the tape while we stuff.... if you tuck your shirt in, stuffing is so much easier as it is a smooth line straight down. So tuck that shirt in!

5) If the painting smock is too short in the arms and legs, do NOT just make the DTD to the end of the smock and email your maker telling them to add a few more inches to the legs and sleeves.
Please understand, we make lots of costumes, so at any given time we have a lot on our minds. It's highly possible we may forget and you'll look silly with your 3/4 sleeve fursuit with built in carpi pants :P If your painting smock comes up short on the arms and legs, grab yourself some paper towel and extend the arms and legs accordingly; it takes 10 seconds and saves the inconvenience of possibly being without a suit when you discover your maker didn't make them long enough and it has to be returned for revisions.

6) Do NOT cheap out on tape.
Seriously.... use Duct tape. Do NOT use packing tape, scotch tape, painters tape, masking tape, dress makers tape, paper tape, ticker tape or any other kind of tape. Duct tape works well because it's super sticky and due to the fabric woven into it it's flexible so it will not warp or distort when you fold it up to mail.
When taping, please be sure to go over the taped person a few times to ensure there are no gaps or thin areas. A thicker DTD is far preferable to a thin one... they last longer and are less likely to fall apart when being assembled/disassembled.

I hope this lesson will assist you in future DTD making endeavours. Now that you know WHY you aren't supposed to do it... don't do it.