As one poster pointed out, make sure the hinges are in line -- shim as
needed. Then, remove the hinge pins one at a time and LIGHTLY grease
with a LITTLE non-migrating grease, like "white lube." Put the pins
back in, and that should do the trick. WD-40 is basically kerosene, and
is good to loosen things up, but is not a long-term lubricant. Regular
oils will bleed all over the place, though a single drop or two usually
shouldn't be a problem. I've had better results with the grease
approach.