Summarize:

Standard fire pits are ideal for burning documents because they stand off the ground and have top covers. This allows for better airflow, which leads to a more complete burn of your documents. Also, it somewhat prevents the escape of document fragments from the fire. Be advised that in most cases it is illegal to openly burn trash in residential areas and cities. In some cases you will need a permit. Check your city specific regulations by searching your state's name and "open burn regulations". Another excellent option is professional burn cages. These are metal cages that function as outdoor incinerators. Burn barrels are another option. Steel drum barrels of 55 gallons are the most common, and will do a better job of keeping document fragments within. However, it is not recommended to use as they produce harmful toxins, and their use is illegal in some states, such as Illinois. It may also be safer to burn the individual piece inside of a cast-iron bathtub. Make sure that there is nothing in the bottom, such as plastic foot grips. This way, if it does somehow manage to get out of control, you have the tub with a ready supply of water. . It is generally easier to start a fire if you begin with kindling (smaller pieces of wood that are easier to burn), and paper. You can even use the sensitive documents as fire starter. Once the kindling is lit, add progressively larger pieces of wood until you have a stable burn. For your safety, there should be no flammable shrubbery, paper, or material of any kind around the fire's perimeter. To guarantee fires accidentally start and spread beyond the fire pit, pour sand around the perimeter. It is also advisable to place stones around the firepit. If you are having trouble getting the fire very strong, use lighter fluid. Be careful not to drop the bottle in the fire or spray too much at once. It is possible to create large explosions and bursts of flame that could injure you. Stand further away from the flame while spraying the lighter fluid to avoid singing your face, chest, and arms. Don't dump them all at once; this could cause small pieces of information to fall by the side. Burn individual pieces, holding them with metal tongs, to ensure they are completely burned. Once the fire has been burning for a while it may have a stable heart (center of hot embers). With a stable heart, you can place more of the documents in at once and allow them to burn, protected by the wood. When burning, proper ventilation is important, not only to avoid smoke inhalation but also to ensure a full and proper burn. The open grate of a fire pit allows for this ventilation; so does limiting the amount of paper you insert at once. Watch the make sure no document fragments are blown from the fire. Even small amounts of information could be the exact valuable pieces other people desire. Burn the sensitive documents along with other pieces of scrap paper. If by accident a part is not burnt, the remains of the scrap paper mixed in will help confuse anyone who tries to read your information. Once you think everything is burned and the fire is out, shift through the ashes and look for any unburned paper. The easiest to spot will be paper that somehow still has a white sheen. However, also be on the lookout for pieces that have turned grey, but still have legible text. Even these must be burnt more completely. Gather all the sensitive debris and store it in a safe, closed compartment until you have the fire burning again. Using protective fire gloves, or long metal tongs, securely place the document fragments in the fire's center. Wait for the fire to go out, and for the ashes to cool to a safe temperature. Using a shovel, gather them in a bag that will not rip. If you have a yard, scatter the ashes evenly throughout your yard. It is also possible to use a small amount of ash in composting units (so long as you did not use lighter fluid to make the fire). Ashes spread around garden plants discourages slugs and snails. It is also beneficial to pour ash around the base of hardwood trees.
Set up an outdoor fire pit. Start a fire Place the sensitive documents in the fire. Check the ashes. Burn any remaining pieces. Scatter the ashes.