Ignition/keyed lock problem

[RGuzz]

Hi,
Lately when I put my ignition key in the lock I have trouble getting it 
to turn...last couple of times it took me several minutes of 
manipulating the key to get it to go. Long enough to make me think I 
might be stranded. It appears to be the original lock as all keys are 
the same. Has occurred rarely, and intermittently, for a year or so. 
Now more frequently.
Pops back easily. Doesn't seem to matter if the steering wheel is 
locked or not.
I know this is a common problem and that there is probably info on this 
that is archived.
Any suggestions?
Thanks.
Richard