Make it easy to communicate and interact with you.
You can take a hard line on many issues, you can set many boundaries. You don’t have to compromise on important values. That’s not what I mean by “easy.” I mean it quite literally: make it easy to talk to you.
How? Simple. State your terms. Be clear about what the ground rules are for interacting with you, and be clear about what you mean by things that you say. Don’t be cagey; there’s no need.
The more candid you are about what it takes to interact with you, the more at ease people will be in doing so. No one wants to walk on eggshells or risk offense. If you make it clear, early and often, that you’re someone who doesn’t play conversational games or take someone’s accidental faux pas uncharitably, then you will find more people – and more honest people – will interact with you meaningfully.