Is it old or is it old junk?

There are lots of shows on TV these days where they find stuff in attics, garages, barns, junk yards, flea markets, storage lockers, and the like.  Some things are junk and some things are gold.   However, when I look around my house I see lots of old things.  Are they old or just old junk?  That is the million dollar question.  What is worth keeping?  Should I run to eBay and find the value on every item that is stashed away on a shelf or in a box in the basement or attic?  Is it worth more if I clean it up or in its natural state?  I do have a few items that I know have some value.  I have lots of baseball cards dating back to when my son was born in 1987.  I have stamps that I started collecting after a trip to Ben Franklin's Post Office in 1972. At least the stamps will always be worth their face value.  Someday, after I retire, don't be surprised if you get a birthday or Christmas card with a bunch of old stamps on the envelope.  My in-laws routinely drop "stuff" off at our house when they visit.  I plead with them not to bring anything to leave behind....but they do not listen.  We have accumulated items from my wife's grandmothers house (mothers side), grandfathers house (fathers side), uncles house (fathers side) and her parents house.  I have no idea if any of it is valuable.  I do have an idea if any of it is hideous to look at.  Maybe we need to take a trip to Vegas.  For two reasons; 1) maybe we can pawn a few items at the Pawn Stars place, and 2) what happens in Vegas stays in Vegas.  So maybe some of this junk can stay in Vegas.