Choose the records you actually use
Start with the sheets that support real decisions: customers, open enquiries, orders and payment follow-ups. Identify who maintains each one and which columns the team uses daily. Keep an untouched backup of the original files. Moving every abandoned sheet into a new system can carry old confusion into the new workflow.
Agree one meaning for each field
Make phone numbers, dates and customer names consistent. Decide how duplicate contacts are identified and which record should be kept. Define a small set of clear enquiry stages rather than importing every spelling of the same status. Map spreadsheet columns to CRM fields, including the person responsible for each customer or task.
Import a sample, then reconcile
Try a small sample containing ordinary records, duplicates and incomplete entries. Ask the staff who will use the CRM to check it. Compare record counts and relevant totals with the source files before the full import. Set a clear handover point so changes in the old sheets are accounted for, then teach the team its first daily routine.