[header] How to be sincere [title] Use sincere body language. [step] Body language can convey a great deal about your attitude, and it can easily reveal sincerity (or a lack thereof). When you interact with others, try to be mindful of your posture, mannerisms, and behavior. 
[substeps] Make steady eye contact, but don't stare. Look away every now and then, and don't forget to blink.