1) Provide us with a flattened .dxf file with bend allowances already in.
2) Check all your hole sizes against PEM catalogues to confirm they are the right size.
3) Make sure all lines are closed and that lines don't just go off in space and stop.
4) Ask for bare metal, no finish.
5) If there are fasteners, specify ones that are in stock.
6) If it needs powder coating or other finish, can you live with the colour they are running to avoid set up times and minimum charges.
7) Tell us you will accept the part as is, you will take responsibility for any CAD errors you put in.
8) Put tolerances, material type and thickness, part number, revision number and any finishes on the drawing.