Here’s is a simple tip that was new to me.
There are two ways to add a vCard with your contact information to a Mail.app signature.
An old post on macOSXHints details how to add it 
as a hyperlink to a remotely-stored vCard file, so that recipients can download it into their Address Books easily.
The end result is nice and clean and saves bandwidth:
If you don’t give two figs about bandwidth, you can simply export your card from Address Book.
Then drag it onto a signature in the Signature pane of Mail’s preferences, and your vCard goes out with every signed email:
Of course, it is possible to share more information than you mean to or more than your recipients want. It might be a good idea to create a special Address Book card for this before exporting it.
