Choose the correct envelope size for the letter
Write the recipient’s name and address on the front of the envelope
Include the recipient’s apartment/suite/unit number if applicable
Add the correct ZIP/postal code
Write your return address on the back flap or upper-left corner of the envelope
Insert the letter into the envelope and seal it
Add the correct postage using stamps or a postage meter
Affix the stamp(s) in the top-right corner of the envelope
Drop the letter in a mailbox with outgoing mail or take it to a post office
Keep the receipt or tracking number if you use tracking or certified mail