Follows are simple instructions for putting together a rolling workbench.
Step 1: Get Rid of Your Old Desk
Put it on Criagslist and greatly under-price it so that someone will actually buy it.
Step 2: Go Get Stuff
(x2) 48" x 36" x 3/4 plywood board
(x1) Set of adjustable bench legs
(x4) Locking casters with threaded rods
(x1) Miniwax Water-based Polycrylic
(x1) fine grit sandpaper
(x1) power drill with misc. drill bits
(x20) 1-1/4" wood screws and washers
12" x 48" and/or 18" x 48" plywood board for storage shelves
Misc. nuts, bolts and washers
Step 3: Mark the Holes
Step 4: Drill
Step 5: Fasten the Bench Legs
If you don't plan on adding shelves underneath later on, Hiroak has this to say:
You need to support the legs like the one with the shelf. If you are rolling that baby around and hits something your legs will fold under using wood screws. You should consider using carriage bolts and counter sinking them, then fill the holes with harding putty for a smooth surface.
Step 6: Attach the Casters
A standard counter is around 34" - 36".
Step 7: Sand
Brush it off when you are done.
Step 8: Seal the Workbench
Stir your finish and apply a thin coat in one direction (either horizontal or vertical). Wait for it to dry.
Once dry, lightly sand it and then brush it off. Apply another coat of stain in the opposite direction that you did with the first coat.
Repeat this process alternating brush stroke direction four or five times.
Step 9: Add Shelves (optional)
I didn't bother to finish the shelves or do anything too fancy with them. Basically, I drilled some holes in the plywood and bolted them down. It's not the prettiest, but it gets the job done.