We're just over the boarder of Samhain and there is no better time to seek protection for the diminishing of the light.
This topic is a huge subject matter. For thousands of years our ancestors have been devising all manners for protecting themselves. Various civilizations grew into large entities through their ability to protect their race religion, or group. Their way of living was defended often through their ability to protect belief and culture. As well, many civilizations fell through the lack of ability to protect.
Many built huge defense walls. Trained armies to fight various invasions. Aside from the apparent dangers of different groups of people invading. They developed strong spiritual protections. Today many might view these as superstitions, ridiculous myths which are old and out grown from modern societies. After all we've come such a long way from such trivialities. Haven't we, or have we?
I think many of us are in many ways just as superstitious as we ever been. Many people wear charms, carry good luck amulets, or wear the same outfit to a sports game. Some wear or use many of these items to protect them as well. We cross ourselves to ward off or bless our intent. We carry rosaries, beads or other forms of protection to bless us and keep us from harm. We pray for protection, seek salvation through our faith or belief systems. We anoint, bath, sprinkle with water, disinfect, or spread salt around our homes or doorways. Gone surely are the days of hanging garlic around the home to protect us from evil.
So what are some of these manners of protection according to the ancient wisdom of some of our ancestors.
Warding: This protective technique has been used for thousands of years. Warding is a sense of creating an imaginary barrier between whatever you want protected and whatever you want to keep out. To ward, to keep safe. Generally speaking warding was used to protect yourself or living quarters from evil spirits, which could threaten individuals or bring bad luck. In ancient times there were threats of invasions, ransacking pillaging or any other form of attack which could strike at any possible moment. Of course they built walls in some cases, but they also protected those walls through other forms of protection. Barriers were established through ceremonies or casting spells. Individuals whom were considered to process the power to establish wards were considered valuable in society. Druids, priests, high chiefs, medicine men or women possessing abilities (often considered to be healers, wise women or witches). Some of their techniques often involved salt, water, incense, herbs, earth elements, vinegar oils or candles. Many involved chanting spells or a verbal intent or rituals putting forth some intention to a God, Spirit or the universe.
Energy: We have energy everywhere in our universe. It is in my opinion a readily available source of power. This energy is often considered the "light". If you close your eyes, allowing your mind to visualize a white light hovering in front of you. This light energy can be used for any form of protection. We can move it. Create bubbles around ourselves, or our homes, our families or other individuals. We can create a barrier between ourselves and others by creating a white light to surround ourselves in order to protect us from harm including the harm of disease. It is often said that when the light is created around something, others can no longer notice or recognize the item it's encasing. Thus preventing intrusion into. A strong wall of protection is established. Negative energy cannot penetrate through white light energy. Of course this hasn't been scientifically proven, as our ancestors just simply knew and trusted various techniques. This source of energy is often used for healing. One needs to visualize this energy penetrating the area of distress so it can heal the ailment or simply use to protect from ailments. Prayer, verbal exchange or music is often involved with this type of energy work. Considered to be seeking higher assistance through God, the Source, God's, Goddesses, Angels, Guides, Spirits or other sources of higher power. Of course many believe the white light is of God or other types of entities.
Angels & Spiritual Guides: Yes, I believe in higher entities. Of course this is a personal choice or belief on an individual basis. Throughout the ages, various higher spiritual entities have been mentioned throughout history. Including Saints.Stories of rescue, protection, or salvation (which is also a form of protection). People whom had after death experiences often mention seeing Angels or Guides or God when they return to the living. Many of these are a guiding force to assist us on our journey through life. We look to these higher beings as a source of light, guidance, enlightenment, faith, religion or psychic abilities. They are often mentioned when initiating spiritual activities for protection against evil or negative forces.
Charms, Amulets: These are items we create, using various protective materials in order to create a barrier between what is ours and what we do not desire to encounter. Usually they are carried with us or on us. However, they can also be placed within a home, property, vehicle or any other space which is deemed to be needing protection. We consider items to be ours, by way of purchasing, inheriting, being born with(self or children) connecting with (marriage) or finding.
We often feel we need to protect these items from harm, bad luck, evil or theft. Several techniques are used to protect us in this manner. We create or use materials that are often related to the five elements. Earth, Water, Air, Fire and Metal. Various techniques use these elements in conjunction with the Universe. Like cycles of the Moon, planets or Sun. We can also incorporate numbers or colors into the mix in order to achieve our desired effect of protection. In fact many magick spells involved these items.
Many herbs are associated with protection: People use to planet various herbs around their property to protect the land or home. A hedge to mark the boarder between this land and the next. Such herbs might have consisted of Agrimony, Dandelion, Blackberries, Angelica, Heather, Peony, Primrose, Lilac or a Raspberry bush. Also seek an Aloe Vera plant inside to create some harmony of protection or keep a string of Garlic hanging by the door. Perhaps you need to cook with some Basil, Dill, Fennel or Thyme or seek a hot cup of Spearmint Tea. Set some flowers out of Carnations or Chrysanthemums and draw a hot bath with Lavender or Jasmine. 
Protection always involves lots of light. The Full Moon or the light of the Waxing or Waning Moon will do. Look to the south and seek the four elements of Water, Earth, Air and Fire. Salt water, or incense will do nicely. Perhaps you would like to sprinkle some around your home, land or items you wish to protect. Don't forget to anoint your candles with oil of protection, Frankincense and/or Myrrh. 
Crystals and Gems: These have adorn the nations for centuries in a display of protection from harm. We also incorporated them into protecting our personal belongings, our land, and home. One can create a grid of crystals to protect the land or boarders between lands. We can do this either by visualizing them there or actually putting crystals in various places upon the land for protection. Many would carry a crystal to bring them protection while travelling, like Tiger's Eye. Try some Tourmaline, Turquoise or Emerald for protection. Don't forget the White Diamond, which states I'm yours to protect forever, or the Red Ruby if one was lucky enough to have one lying around.
Smudging: This is an ancient practice used in many civilizations in one form or the other. Still often used today. Essentially, it's using a system of burning various dried herbs or incense to clear out negative energies. It is sometimes believed that negative energy collects within a space or around the aura of an individual. Thus if one burns creating smoke, it will remove this energy. Items often used are a shell, which represents water, a herb which represents earth, fire is created when you light the herb and the smoke represents the air. This was often used in the ceremonies of ancient Native tribes as well as in Native American people's. Many other cultures smudge through incense or other burning rituals. This form of ridding negative energy is used for protection, acknowledgement and driving away negative energies. You can surround a person with the smudging technique to remove negative energy around them. 
Animals:Of course we have been very attached to our pets throughout the ages. Seeking protection always incorporated having a trusted animal by our sides. The first animal of protection is of course the Dog. This animal has existed in ancient cultures for thousands of years. From the Egyptians to today.This animal was often a symbol of protection for mankind. There are of course other animals which were also considered to be of protection, such as the Horse. The Elephant was considered protective as well as lucky in some cultures, along with the Monkey. Don't forget the Tiger nor the wolf or wolverine either 
Depending on the culture or history, many birds were also considered to be of value in protection. Having a peacock or quail feather in the rim of the hat one was wearing. A Raven might grace your home by leaving you his feather upon your doorstep. Lets not leave out the crow or the duck, common birds to the average environment. The crow was also considered to be a bad omen for some cultures. Feathers are often used in various protective ceremonies, worn as adornments of protection.
Spells: Many a spell has been derived to keep out the evil and ward off those whom might seek to take advantage of an opportunity of convenience. The ancients used all manner of spells to repel eliminate and protect one from harm. Various plants or elements were believed to hold the power to save one from the evils of harm. Combining various elements together held even greater power of bewitchment or salvation. A wreath hanging on the door could hold the power to ward off evil entities. Perhaps a cinnamon stick or some Black Snake Root. No doubt you've dropped the bay leaf in the soup a time or two. Maybe your eager to cast a circle around you with a hazel bunch as the Celtic traditionally have done. 
All manner of spells or amulets have been given to men going off to war. Such as the blessed scarf of a lady waiting for her man to safely return. The fisherman setting out to sea. A wife home with a black cat to ensure safe passage. A farmer practices his traditional protection for the crops he's planting. Weaving sheaths in various patterns or planting according to the Moon's cycles. 
Protection is as important today as it ever was. Practices have been passed down through the ages from our ancestors to us. Many practices we do unconsciously because our grandmother use to do it. Mother's blessing their children with protection through a little gift to keep with them. Protecting us from the harms and evils of the world.
 Complete Book of Correspondences: Llewellyn's; p.112-113
 The Element Encyclopedia of 5000 Spells;p.876
 Superstitions & Symbolism: Internet
 Wings for the Spirit: Internet
The information is a highlighted version of this massive subject.