Appraisal Approach
  
You go to a garage sale and find a box of old baseball cards for sale. You assume most of them are trash, but you harbor some hope of finding a lost treasure. How do you go about figuring out which cards are valuable and which ones should stay buried in the box?
Time to figure out an appraisal approach...
The appraisal approach describes the process for figuring out something's value. It's basically the formula you are going to use to determine how much something is worth. You might take into account the quality of the item, what other similar items sold for, how hard it would be to sell, etc.
Rather than just eyeballing the item and guessing at the value ("I love Leon Durham! I'll trade you my car for this card!"), an appraisal approach presents a more scientific process to determining value.