If you know you're not going to run it for 3 or 4 months (like over a winter), then I'd run it dry (burn all the fuel out of it), then put in quite a bit of light weight oil. Air tool oil, or sewing machine oils are good.

If it will be stored for a year or more i'd do the same thing, but remove it from the plane and seal it in a Zip Lock type bag.

If it's just sitting in the shop unflown for a month or so, don't bother. I agree with Minnflyer about after run oil too.
Dennis-