Separate "cast" aluminum (like engine parts) from "sheet" aluminum (like siding or cans).
If a brass valve is attached to a copper pipe, cut them apart. If left together, you will likely be paid the lower brass rate for the whole piece.
To qualify as "#1 Prepared Steel," pieces usually must be clean, at least 1/4 inch thick, and cut into manageable sizes (often 3 feet or smaller). Typical Scrap Metal Prices (Estimated)
Bare Bright Copper (stripped, shiny wire) is the highest-paying grade. #1 Copper is clean pipe, while #2 Copper has paint, solder, or corrosion.
Strip off plastic handles, rubber hoses, or fabric.