Try new keys with the door open: This way should they get stuck or not work, you won’t be trapped outside or with
your door shut. While a broken lock is never great, a door is probably more use when open than it is when closed.
Attempt to protect a lock from weather if possible: It’s not always possible obviously, but small things like keeping your door in an alcove or porch can make a big difference.
Call a locksmith as soon as you notice problems: Whether the lock is simply stiffer or it doesn’t make the same clicking noise when operated, by dealing with the problem quickly you can prevent it leading to a break in or a completely broken lock that will need to be replaced and leave you trapped outside.
Be careful with keys: Don’t throw them around or drop them down carelessly or you will risk causing them damage and even snapping them. The small indentations on the key blade are very precise and necessary for the key to work so make sure you don’t damage these.