[header] How to do a mail merge [title] Build a data file. [step] This can be a spreadsheet file, database file, or even a text document with the proper formatting. Spreadsheet files are most commonly used; this guide assumes you are using a spreadsheet. 
[substeps] Your data file should have all the information that will have to change from copy to copy. For example, if you're writing a form letter, your data file will hold the names and possibly the addresses of everyone you intend to send the letter to.