ANSWER - A poppet is simply a representation of a person that you wish to cast magic on. Normally it will resemble the basic outline of a human and more often than not, at least when practical, it will be personalised in some way relating to the individual focus of the spell work. The artistry involved in making the poppet isn't important - by which I mean it doesn't have to physically resemble the person you are doing the magic for - although incorporating very basic features may help you to make the link between the person and the poppet in your mind.
What a poppet is made of is generally unimportant (though different traditions may have their own ways of doing things.) A poppet in olden times would likely have been sewn from old cloth or rags and stuffed with straw. Cotton poppets are still used today - funnily enough I was just suggesting to a fellow witch the other day that we put some of the coming winter aside to stitching a few basic poppet forms so we have them to hand when needed.
Another traditional method of making poppets (sometimes referred to as dolls) is shaping melted wax to resemble a figure. This can be trickier than it sounds and not always the most pain free method of doing it! The modern equivalent I usually use is plasticine (or on the odd occasion blue tak!). However the chosen material may be relevant to the individual spell. A wax poppet may be better suited to weight loss spells (melting the poppet of the individual to reduce their mass) whereas a cloth poppet might be better for taking a person down a peg or two (dropping from a height... lol).
For the less crafty witch pre made poppets can be adapted from cheap children's dolls or even second hand Barbies. The only limit is imagination...
Nothing to stop poppets from being carved from wood and nature itself yields natural shapes than can be used as "living" poppets - the roots of the Mandrake plant have traditionally been used for this but those of us with a less successful track record in gardening may prefer to use dandelion roots...
A poppet can be personalised in a variety of ways. Attaching a taglock like a lock of hair is probably the most common but some people can be irritatingly reluctant to hand over their hair in which case you may need to get creative. Toe nails, urine, blood, excrement, semen, anything personal will work just as well. Failing that cutting them out of a picture and pinning it to the poppet could be a useful substitute. In the absence of anything at all carving the name of the person into the poppet or writing/painting it on may very well be enough.
Poppets seem to appear a lot in books concerned with the negative elements of magic, cursing in particular. But use the poppet in itself is neither black nor white magic and there is no reason why a poppet cannot be applied to healing as well as harm. I've used poppets recently in spells as simple as drawing an individual toward the light (tying string round the poppet and pulling toward a candle), protection (wrapping the poppet in bubble wrap and placing in a charmed jar) and reducing stress (burying the poppet under a pile of pebbles representing the worries weighing the person down and then lifting them off one by one). No reason to believe poppets can only be associated with dark magic. Poppets, as with most magics, are neither dark nor light, merely a reflection of the caster's intent.