some email providers will allow you to alias your email automagically. For example, google. So, let’s say your email is firstname.lastname@example.org. start signing up for services (facebook, randomwebsite.com) with your email, but add a `+` sign to your email address before the `@` So, you would use email@example.com and firstname.lastname@example.org
what comes after the `+` isn’t important, but what happens is, if you get an email from siteyouhaveneverheardof.com that is addressed to email@example.com then you know that randomwebsite.com is selling your data and you can do with that what you want (read: slander them publicly, and cancel your account).
You won’t be affected by the `+` unless you manually type in all your emails all the time. Your email will behave normally and you won’t feel it there, and if you use a password manager (you should) then you don’t type emails anyway.