Inviting users to read your text and actually making them read it are not easy tasks.
The web content accessibility guidelines (WCAG) are a good starting point, but the factors that condition the experience of reading texts are numerous and interconnected: from the physical mechanisms of reading to the cognitive processes involved, to the amount of attention paid.
Web typography best practices and wise font selection could help. Sometimes informed choices and just a few lines of CSS code can make a huge difference.
A readability playground I prepared to let workshop attendees better experiment with the concepts I presented. Full of CSS properties that might affect readability.