If your home's front door lock isn't working as it should, you want to call a mobile locksmith rather than trying to take it apart yourself, as trying to reassemble a lock and fit the pins and tumblers back into place can be more complicated than you may realize. However, before you make that call, note a few things you might need to share with them so they know how to address the problem once they arrive.
1. Note if the lock works when the door is open
If the lock works when the door is open, then the problem is that the door is not properly aligned with the doorframe. The bolt for the lock cannot move smoothly into the doorframe when these two pieces are not aligned. Over time, doors may begin to sag or wood doors may expand and shrink as they absorb moisture and then dry out so they don't hang evenly. Your locksmith can often address this problem by realigning the bolt and doorframe, but be sure you note to him or her that the lock works when the door is open so they know what tools to bring and don't expect to simply change out the lock.
2. Note if the key you're using is a duplicate
The reason this is important is because some hardware stores and other key cutters may not be able to exactly match a key when they make a duplicate. You may have also chosen a low-quality material for your duplicate key so that it gets worn down more readily than the original key. Note this to a locksmith as they will then know that it's most likely the key that is not working, and not the lock itself that is broken.
3. Look for signs of possible tampering
If your door lock suddenly sticks or cannot open and close easily, look for signs of possible tampering. If there are marks along the key slot or on the doorframe, this often means someone tried to force the door open. In that case, it can be good to have your lock upgraded or changed out completely; even if the intruder didn't get in, they could have damaged the lock enough to weaken it and make your home more penetrable. A locksmith can replace the lock and even add another deadlock or whatever else is necessary to make your home secure.