You notice that the lock on your front door sticks now and then, but until it really seizes up on you, it's not a huge problem. The good news is that there are a few things that you can try at home to at least temporarily solve the problem. Try a few of these options to get your lock to cooperate with you.
Clean the Lock
Locks tend to develop a buildup of tiny metal shavings. These shavings are a result of the key and the tumblers moving together. There's nowhere else for these shavings to go, so they collect in the lock along with dust and other debris. To clean the lock, remove the screws holding it to the door and use canned air to blow the debris out of the mechanism. Put the lock back together and it should work much better.
Lubricate the Lock
Avoid using oils or lubricants like WD-40 or penetrating oils. Although they may temporarily fix the sticking issue, these oils hang around in the lock mechanism and stick to any metal shavings and debris. A better solution is to use graphite powder to lubricate the lock. Graphite powder comes in a small bottle that lets you squeeze it directly into the lock. After squirting the graphite powder in the lock, slide the key in and out to work the powder deeper into the lock.
For locks that stick so badly that the key won't turn or slide back out, you have to try more creative means. Put a few ice cubes into a zippered plastic bag and remove all the air before sealing the bag. Hold the ice against the lock, moving it around to different locations after a few minutes. Since cold helps to shrink items, the lock should loosen up just enough to release the key.
Use a Small Hammer
If all else fails and the lock is still sticking, try a bit of mechanical persuasion. Use a small hammer to gently tap the sides of the lock. Avoid hitting the lock too hard since you can damage it. Try the lock again after a few soft blows and see if that corrects the sticking problem. If the first round doesn't do it, try a few more blows with the hammer, but don't overdo it.
If your lock just isn't responding to any at home techniques, it's probably time for some professional help. Call a local locksmith, such as Head's Lock & Key Works Ltd, if you have questions.