AskHistorians

One of the ways would have been Letters to the editor, which were basically blog posts written by individuals who are not journalists, published in a newspaper. Of course the editor had to approve of what you had to say so it wasn't a perfectly free medium.
These existed well into the 20th century even into 1990s.

Going back in past there was the option of nailing pamphlets to churches, however this was highly dependent on having friends with a printing press which was the cutting edge technology for the time.