Before you call me, look in your cupboard. You may already have all you need to fix that sticky lock. WD-40 is the go-to for most locksmiths and an increasingly common item kept around the house. Marketed as a multi-use product, WD-40 is a solvent that also lubricates. A quick spray in the keyway will help to loosen most locks and make the key insertion and turning much smoother. The lubrication continues to protect the lock's internals for months.
In homes by the ocean, especially here on Cape Cod and the Islands, the continuous salt air seems to accelerate the corrosion of, well... nearly everything--including the locks on your doors. Typical door locks and deadbolts are made up of tiny precision parts with close tolerances. Any bit of corrosion can stiffen up its operation and make it feel like the lock is failing. A little bit of locksmith-in-a-can, used sparingly from time to time, can save you some aggravation, and a little bit of money.
Superzilla--The Green Wonder Product, is an award-winning, greener version of WD-40 that may actually serve you better in the long run. Both products clean and lubricate very well, but every lubricant can eventually turn into a slightly gummy residue that locks do not appreciate. Superzilla, in my view, lubricates as well as WD-40 (if not better) and tends to leave no lasting residue to slow down your locks' operations. And... it's USDA Certified Green.
Before you call... try a little squirt of WD-40 or Superzilla. If that doesn't work, you definitely need my help.