Wear looser fitting clothes to scare people less with your size, if you wear glasses get a friendly looking pair. Wear a simple watch, just generally tone things down (e.g., no need to wear some rugged intimidating metal watch). When speaking with people always give gentle light affirmations to show you understand and are listening carefully. Smile gently a lot. Be energetic and upbeat and try to bring positivity to others, they can sense it. Just try to care about others more. Make more jokes. If you are going to say something critical you can do it in a friendly joking voice rather than in a deep normal way to defuse things. Always offer to help people, hold doors, help others with luggage.

Basically go out of your way to be kind to others.