eBay Question for Those Who Buy Stuff There

I have a quick question for all you eBay shoppers out there.
Have you ever used the MAKE AN OFFER feature on an item to try to purchase it?
And if you have, do you have any guidelines for how much you offer for items?

I am just trying to figure out if I am Waaaay off base as a Seller with my thinking on these MAKE AN OFFER situations.....or if I just attract all the weirdos?!? ;-)

Leave us a comment if you will.....much appreciated!

Sluggy