If part of the key is protruding out of the lock, you can use a pair of needle-nosed pliers or tweezers to gently turn the key in the lock to open the door. If the key is fully inserted into the lock, you may also be able to use a key extractor to help turn the key into the unlocked position. 

But if the key breaks off halfway into the lock or you simply can’t reach it to help engage the unlocking mechanisms, you should probably call a professional.

The best type of deadbolt depends on your specific needs. If accessibility is your primary concern, a single-cylinder deadbolt is the easiest to operate. Mortise locks are likely the most secure type of deadbolt you can install, but single-cylinders combined with secondary locking mechanisms like vertical locks are also a great option. Smart locks will give you the most flexibility to open and close your locks whenever and wherever you need to. 

Begin by checking the power source, typically a battery or wired connection. Ensure the battery is installed correctly, has sufficient charge, and isn't corroded. If it's a wired lock, examine the electrical connections to confirm they are secure and free from damage. Additionally, inspect the lock's programming or settings. Confirm that user codes or access credentials are programmed correctly and that any remote control devices are paired and functional.

Security experts recommend deadbolt locks as the most secure option for a house's exterior or entry doors. Deadbolts provide the best security because they can prevent most types of forced entry and are harder to lockpick. Common types include the standard single-cylinder deadbolt, which is often found on front doors. For enhanced security, you can opt for a double-cylinder deadbolt, which requires a key to operate from both the inside and the outside.