Smile, eye contact, acknowledge others' existence, firm handshake, good posture, confident walk, act like you know what you are doing and are supposed to be there. Be polite to others, listen, respect them, have deference to others when appropriate. Say please and thank you. When talking to an adult stranger, give them a title (like Sir or Ma'am) even (especially?) if you feel they are "beneath" your social standing.
Maybe these rules only apply in the South? I have described the charismatic "good ole boy" that seems to climb to the top of the dung heap (socially and politically, particularly on the right), often without real merit other than charm.