Magick is not a good or bad in itself. Magick is like a tool. For example, we have a gun. The good thing to do with the gun would be to hunt with food. The bad thing to do would be to shoot another person. There are always going to be people who misuse tools.
With the sheer number of practices, styles, and philosophies out there, it is usually fairly safe to say that magic becomes what you want it to be, and is performed the way you want to be performed. Walking a magical path is an exploration of personal philosophy combined with the study of history, cultural lore, natural processes and cycles, and forming personal and symbolic connections between them to effect change.
Ihere are some who involve blood with ritual practice, usually in small ways like anointing something with a drop of blood to form a deep personal connection. Or placing a drop of their blood in a chalice or bowl combined with other ingredients, or other symbolic ways to put action to the desire of commitment or personal link with the magic being performed. But it is a matter of personal choice because it is how they personally feel the most connected with their intent.
For others it is through using a specific tool or symbol like an athame that they have personally blessed. or by laying offerings like hand-made breads, honey, wine, grapes, or personally crafted items to be involved in the working.
Still more simply connect with their magic and energy through meditation and visualization. or by only working magic during times of high or imbalanced energy to set things more easily into motion. Like new or full moons. equinoxes, dawn or dusk, or personally sacred places.
usually it begins as a philosophy of self discovery, introspection and inward searching. By learning to understand yourself, you learn also what you best connect with and that then helps guide you into the kinds of magic and practices and deities or entities you find a rapport towards. And so it comes to end up with you finding a personal style and practice inspired by others, guided by information, decided by introspection, but defined by yourself.
You don't have to. There are some practices which are rumoured to have an involvement in such acts, but these don't necessarily have anything to do with 'witchcraft'.
LOL drink peoples blood, oh thanks for that laugh. no you do not. [for a number of reasons] witchcraft is simply a craft where you observe and work with the cycles of nature. you could cast spells, but it isn't required. it's more observing the changes of the seasons and living in balance over ghouls and monsters.
i suggest picking up a copy of The Witches Bible by Stuart and Janet Farrar or The Complete Book of Witchcraft by Raymond Buckland to help you get started on real witchcraft. the vast majority of pop culture doesn't know what real magick is. we do not drink blood, sacrifice babies, worship the devil, fly on broomsticks, transform into cats, turn people to toads, or shoot lightning bolts from our wands. there are many paths in this Pagan umbrella that follow some form of witchcraft, but at it's core it's a peaceful path of balance and nature. those who cast spells [because spell casting isn't exclusively witchcraft, there are witches who don't believe in spells] do so believing we are tapping into a natural energy to bring a desired change. rarely do spells require blood or living sacrifices. yes, there are some forms which follow these things, but it's not mandatory and if you don't want to, you don't have to. your path, your choice. [i've been a witch for 13 years and have never used animals or blood in my spells because it's just not my thing]