Regularly backup the data on all computers. Critical data includes word processing documents, electronic spreadsheets, databases, financial files, human resources files, and accounts receivable/payable files. Backup data automatically if possible, or at least weekly, and store the copies either offsite or on the cloud.
I keep coming back because you get my computers fixed, are honest, and great with follow up questions! Keep your eyes on your customer service and you will be in business for a very long time!