The Month of Letters. Make sure to gather your addresses and put them in your address book.
If you don't have an address book, this is a good time to start one.
In the olden days, we'd write them in notebooks and place them near the "main" phone outlet.
Times change, and so do phone "books." If it's easier, include addresses in your cell phone; contact lists often have fields for mailing addresses.
E-mail contact lists also may provide fields for mailing addresses.
Be sure to include the ZIP Code, if applicable.
Finally, make sure you address envelopes or postcards properly. Visit the U.S. Postal Service website for information.