Decide what you will be storing in your safe. The quantity and size of items as well as the physical material they are made of will make a difference when choosing a safe.
Decide the necessary size of the safe. If the items you want to store in a safe would fit into one size, choose a size a bit bigger to make room for future items. Use a measuring tape to measure the shelf or other place where you will be keeping the safe.
Choose a fireproof rating that will meet your needs in a disaster. If your safe is kept in an area of your home that would be engulfed in flames for long periods of time in the event of a fire (like the bottom floor of a home), you will need a higher fireproof rating. An example of a very high fireproof rating is two hours.
Choose a lock type for your fire safe. Combination, key or combo lock designs are common. If you are also guarding against burglary, try a combination lock. Thieves can find keys, but they are less likely to discover a memorized code.