Use a cordless reversible drill fitted with a 1/4-inch socket bit to remove the screws from the trim pieces around doors, windows and any other trim.
Remove the windows and doors to the building and their casements and jams. If they were secured with screws, unscrew them with the appropriate bit in the cordless drill. If they were nailed into place, loosen the casing or jam slightly with a crowbar, then saw the nails off between the casing or jam and the beam or framework with a reciprocating saw.
Put each screw in a nail pouch as it's removed. Don't concern yourself with sorting by color or length. They shouldn't be reused.
Cut any caulk with a box cutter that was applied to seal windows and doors, then remove the trim piece.
Mark where each piece of trim fits with a permanent marker on the back side so the mark will be invisible when it's reinstalled.
Remove any rain gutters and mark them so they can be reinstalled in the same positions they were removed.
Use a ladder to access the roof and always wear a safety harness to keep from falling when working on a roof.
Start at the peak, removing the top cap first by unscrewing the quarter-inch head screws securing it.
Remove the screws that hold each 3-foot wide section of sheet metal working from the top down. Each of these sheets should be identical so there's no need to mark them but if you have one or more that is different, mark them so they can be reinstalled in the proper location.
Stand on a ladder to remove the final row of screws at the bottom of each sheet of roofing, then lower the section to the ground.
Remove the sections of sheet metal from the exterior walls by unscrewing the 1/4-inch head screws securing them. Start at the top using a ladder, if necessary, working your way down until you are standing on the ground. Then, switch to the lowest row of screws and work your way up so the row of screws about waist high is the last ones removed. This will facilitate handling and stacking the removed pieces.
Mark any unique pieces of siding. Most of the sections will be identical, but those cut to fit around doors, windows and on the gable ends of the building will need to be installed in the exact spot they were removed.
Use a sledge hammer to loosen the nails holding all the purlins and all but the topmost girt to the trussed rafters and side walls. Purlins are the roof support boards to which the roof sheeting was attached. Girts are the boards to which the side wall sheet metal was attached.
Use a crowbar to remove the nails or a reciprocating saw to cut the nails off to free the purlins and girts from the structure.
Stack the purlins and girts according to length. Most will be the same length and won't need marking. Some of them will be cut to specific lengths and you will need to mark the boards and where they were used.
Chain the end rafter truss to a raised front end loader to support it while the truss is disconnected from the top girt using the same method used to free the other lumber.
Lift the truss free and carefully lower it to the ground.
Continue on down the row of trusses, removing each one in turn.
Remove the top girt.
Use the front end loader and chain to uproot each of the poles that supported the structure. Most of these will be the same length. Mark any which are odd size and note exactly where it will go during reassembly.
Use the sledge hammer to knock off any concrete used to stabilize the poles.
Move the disassembled parts to the new building site.