The concept of the Witches Bottle is quite old. It is essentially a bottle buried at the furthest corners of one's property and filled with unpleasant and downright harmful items used to ward off hostility. In a pinch (if you lived in an apartment for instance), the bottle(s) could be hidden in a cupboard, under floor boards, in a potted plant, etc. Use your imagination. Generally only one bottle is necessary, this to be placed in a central location such as a hearth. However, since the hearth (fireplace) is no longer central to the design of most buildings, this location could be replaced by the kitchen or somewhere near or under the door through which most people enter your home. If you are not sure from which direction danger might appear, consider a grid of bottles, one for each cardinal point or corner of your property and one in a central location to tie it all together. The central bottle should contain a magnet to make it more like the center of a compass .
What you put into the bottle is dependent upon your imagination and what you have on hand. Some of the contents should come directly from the person or people to be protected. This is by far the most repellent aspect of the spell, as it should be. You want to fill your bottle with things you would not want to encounter in an everyday setting. So if your companions are agreeable to it (and you have a strong stomach), you'll want their feces and/or urine and even (menstrual) blood. Less disagreeable to collect would be a bit of saliva, hair, fingernail clippings, or a small bit of fabric. This is all to focus the spell on the people living in your home and protect them from all comers.
The more dire your situation, the more aggressive the contents of your bottle should be. You'll want to find anything which might cause an injury to anyone who means you and yours harm. Anything sharp... rusty old screws and nails (careful of tetanus), razors, egg shells, broken glass, mirrors, plates, cactus needles, pins, stones, ashes, wood, bone, etc. The only limitations on what you might put in the bottle comes from your own imagination.
Finally, the symbolic aspects of the bottle. Red string is a common ingredient, it being protective in many cultures. Knotted thread is also common. I could write an entire post on knot magic alone, but in this case, the knots are meant to bind whoever comes your way from doing any further harm. Herbs are common, particularly rosemary which was used to make your enemy forget their grudge. Sand to weigh your enemy down, wine or vinegar to drown him, salt which was both defensive and offensive (salt in your enemy's wounds or eyes), etc, etc. Anything you can symbolically justify placing in the bottle is good.
NEVER OPEN THE BOTTLE OR DISTURB IT ONCE IT IS SEALED AND HIDDEN. The bottle(s) should remain sealed in perpetuity. You may go the extra length of adding protective symbols to the exterior of the bottle (I like the Ottastafur for this), sealing it with wax, and/or wrapping it in cloth and binding it with twine.
This is my own twist on the idea of the witches bottle. Protecting your friends and family on your own property is one thing, but you can't expect them to stay put indefinitely. That would be a prison of your own making. To extend the protection of the witches bottle(s) beyond your property, smaller personal (mobile) wards may be created for each person involved, and these should be made at the same time as the main wards if at all possible. If you think you might need to make more later for additional people, save the scraps of your initial work... left over needles, nails, wax, string, etc and use that to create a sympathetic bond with the bottles.
In addition to anything which would bind the bottles sympathetically to the larger grid, it's important to include something of the property itself. So, wood, stone, plaster, dirt, or anything which serves as part of your shelter or property. A loadstone (magnet) in each ward is also helpful, and this should be a magnet that was kept with the one in the central bottle for maximum efficiency, making the ward into a kind of compass attuned to the house itself. To enhance this symbolism further, you might paint a compass onto the bottle or use the Vegvisir, an Icelandic compass rune. This will serve the function of drawing on the house's protections for anyone in possession of the ward as well as allowing someone not initially included in the bottles to pass through the outer wards without becoming confused. The compass rune and the magnet itself will always help the holder to come back home.