Without a doubt, there are going to be TONS of people who disagree with the techniques in this post! However, these things work for me, so here goes!
None of my scissors are the expensive, really nice kind that really need to be sharpened by a pro or sharpened on a stone, though I do have some for purposes other than paper that are the "ginsu" type that are not supposed to need sharpening. So, for most of my scissors, I use do-it-yourself methods to keep them in good working order.
I've heard some people use sand paper instead of foil, but it seems to me that might nick your blades and once you have a nick, all the foil in the world won't get rid of it! It is time to toss those babies, have them professionally sharpened, or use them for things other than paper crafting. Better yet -- get yourself a pair to cut wire and any other material that might nick your paper scissors!
Now if I could only find that favorite pair of pink cutterbees -- if I had put them back in the shield where they belong......