If it was going to be for more than a few days, I'd loosen the trussrod a 1/4 turn, make sure the fretboard wasn't too dry, and store it either upright, or laid flat...
I'd do as georgestrings already mentioned and also make sure it's in a dry place. If you are in an area that has high humidity I'd also wrap it in and old towel or blanket unless you are able to find something that could work better to keep it from dust, mold, or anything else.
I would loosen the truss rod completely, then tighten the nut until it is just snug.
The truss rod is there to counteract the tension of the strings. With no strings present it does not need to be tight. If it is, it will tend to induce a back bow in the neck over time.
I would loosen the truss rod completely, then tighten the nut until it is just snug.
+1... that's the proper way to do it. Just store it in a place that is instrument friendly... ie: not in the trunk of your car - or - not in your damp basement.
