How should I prepare one (currently built) LEGO set before selling it? I have a large used LEGO set that I'm hoping to sell or gift onwards (Scorpion Pyramid). It's currently built (and therefore complete, and not mixed up with any other LEGO), but I'm not sure what to do to prepare it for passing on. 


Do I take it apart? (I'm assuming yes)
Do I try to sort the bricks back into build-order bags (i.e. the mixture of pieces that comprised bag 1, bag 2 etc), or do I sort them some other way by type of piece and colour? What would a buyer expect to see?
I have bought several used sets and it's a mix - sometimes people send the entire set built, sometimes split into larger chunks, and sometimes broken apart into individual pieces. It all depends on the current state of the set (fully assembled, partly assembled) and on the dimensions and availability of the shipping supplies. In the US it is easier to break the set apart and fit it in one of the pre-priced USPS shipping boxes that give you a uniform rate.

As a buyer, I always break the sets I receive down to the individual items and then inventory the sets using the full set inventory. Time intensive but it assures me I get the full set, and that there are no short-cuts/substitutions etc.