Instead of using common email IDs like firstname.lastname@example.org or email@example.com, you could use non-intuitive email addresses like firstname.lastname@example.org or email@example.com. This will prevent spammers from guessing your email IDs.
Don't make the life of spammers easy by activating a 'catchall' email account, which allows emails sent to firstname.lastname@example.org delivered to your inbox. Keep it de-activated.
Embed CAPTCHA images in your online forms to ensure only humans are filling them.
Display your email address as an image on your website so that only humans can see it and type them in their email client.