I know a few ways to make them -- basically anything of human shape can be used, and often (but not always) it's filled with herbs or roots of some type, as well as the target's hair or other biological samples. One also can simply write the target's name across the doll.
It's then usual to baptise the doll either in water or by making a mark on its head, to ritually make it 'alive' and turn it into your target.
Also this:
Doll Babies, or "Voodoo Dolls" as they are more commonly called, have a variety of magical uses. Purposewise, they are used as a stand-in for an actual person on whom a spell is being worked, and are not themselves inherently used for evil. They are generally used in a symbolic way that is representative of the sort of effect the practitioner wishes to produce upon their human target. In previous times, they were a virtual necessity for any sort of influencing or commanding spells; however, the advent of photography has put them somewhat on the decline, since photographs are typically cheaper and easier to use. The doll baby still holds a certain place in magic, however; for it is a time-tested and traditional working of the oldest sort. A curse is known from Ancient Egypt in which practitioners would make up such a doll, and after covering it in magical writings it would be wrapped up and thrown into a fire. The ashes would be mixed with dung, and it would then be burnt a second time.
Here are some modern-day spells for using doll babies:
PROTECTION
Some practitioners are known to fix up a doll baby as their own self, putting some hair or bodily fluid into the doll along with protective herbs like ginger and dragonsblood resin. They then command the doll to absorb any curses or misfortunes aimed their way.
CURSE
Fix a doll as your enemy, and fill with calamus root and vandal root, and Crossing powder. Hide this doll on your enemy's property. If you wish to cause specific physical ailments, cut off the area of the doll (leg, arm, head) where you want the person to suffer.
MONEY
A doll can be fixed to represent the practitioner's own self; it is then placed in a drawer or other quiet place, surrounded by coins and money so that the practitioner will always have cash at hand.
MARRIAGE
A somewhat coercive marriage spell using a doll baby involves the practitioner fixing the doll as their intended and dressing it with love and marriage herbs such as orange flower, deerstongue leaf and periwinkle. The doll is then nailed down to a board, and with each strike of the hammer a command is given. At last, the doll should be firmly nailed down: it can't go anywhere, and neither will the target.
RECONCILIATION
A doll baby fixed as the target is dressed daily with Peace Water: the practitioner massages the doll and tells it soothingly to calm its anger and be friendly again.
REVENGE
A doll baby is fixed as the target and dressed with cayenne pepper and sulfur. If the target had done something bad that they should feel guilty over, the interior of a black box can be lined all over on every side with mirrors, so the doll must always look at itself. The box is then taken out to a graveyard and buried. This is said to make the target feel such guilt that it will eventually torture them to death.
WORK
To get a job, fix the doll as yourself and fill it with Steady Work powder and calamus root. Take it to the place you want to work and either bury it outside the door or hide it within the shop, to influence the people working there toward hiring you.