Choose the smallest reliable product master
Start with a representative item set rather than every historical row. Include one ordinary item, a variant that is easy to confuse, a carton-to-piece conversion and any serial or lot-controlled item that is genuinely in scope. Give each item a stable internal identifier and an unambiguous description. Decide who can create a new item and who approves a correction. Old spreadsheet columns often mix supplier descriptions, shelf labels and customer names for the same thing; copying them all does not resolve that ambiguity. The product-master and SKU guides establish the identity rules before barcodes or imports multiply them across the operation.
Make units and locations visible at the handoff
A quantity without a unit or location invites interpretation. Write down whether a receipt is counted in cartons, packs or pieces, and define any approved conversion. Then identify where the quantity belongs physically and what that location means operationally. A returns inspection area should not silently mean available-to-sell stock. Test how the chosen system represents those distinctions instead of assuming a shelf label creates a stock status. The unit, barcode and location guides belong together: a scanner identifies something, but people still need a clear rule for the quantity and destination they are recording.
Decide who can change records and how systems exchange them
Preparing data also means preparing authority. A person who receives goods may need a different permission set from the person who edits cost fields or approves a stock correction. Record roles against actual tasks and test a representative account with the intended restrictions. Map each integration separately: which system owns the item, order, quantity or accounting entry, what triggers a transfer and what happens after an uncertain response. The permissions and integration-boundaries guides help expose gaps before go-live. Do not use a broad administrator login as the everyday workaround for a configuration you have not yet understood.
Open with a count and a reversible cutover plan
An opening balance needs a defined moment. Agree when the count applies, how later receipts and shipments will be recorded and who can approve differences between the old record and the physical count. Preserve the original import file and a controlled record of transformations. Try a bounded sample before introducing the complete master, and verify both records and quantities after import. The opening-stock guide distinguishes physical truth from historical clutter; migration-cutover connects that result to the first live orders. A fictional ten-item pilot that reveals one unit mismatch is useful progress. It is a reason to repair the mapping, not a reason to multiply the error across a thousand items.