Sticky locks are a common problem, but WD-40 is not the best product to use.  While it is a wonderful product for water displacement, and a fair penetrant, it leaves a lot to be desired for lubricating locks.  When we service locks here in the shop, they are chemically cleaned then lubricated with a synthetic grease designed just for locks.  It is not available to the general public.  Our favorite lubricant that is readily available is TriFlow.  We find it to be quite good.  Many hardware stores sell it, and as do a lot of bicycle shops.  Please do not use graphite.  It combines with grime, metal particles and moisture to form a goo that sometimes cements locks in place.
 
Note that the split tumbler series of Toyota locks are quite prone to issues that can cause them to be quite unruly with moderate key wear.  A correctly cut key will solve problems many times with those locks.  Just duplicating your key will not give you a new key; it just results in a worn out key on new metal.  A locksmith can code cut a key back to new key specifications.
 
Steve Sandlin
Registered Locksmith