Create an encrypted message, then send it to me however you like. Only I will be able to read it.
curl https://www.andrewbruce.net/key.asc | gpg --import
Ensure it wasn't tampered with:
gpg --fingerprint email@example.com
The output should include the fingerprint I publish on e.g. Twitter and keyservers.
Write a message:
gpg --encrypt --armor --recipient firstname.lastname@example.org
Hit Ctrl-D when you've finished, then send the text between and including '-----BEGIN PGP MESSAGE-----' to me as an email or via any other means.