Always stand by your word.  Take your vows seriously.  If you promise something, be sure that you do it.

Jesus tells us to say yes when we mean yes and no when we mean no.
You don't have to "swear to God" to be more believed.  If a person doesn't believe you, you cant change their minds by "swearing to God".

Always tell the truth.  Never stretch or exaggerate the truth.  Never lie. Always say yes when you mean yes and no when you mean no. That would make Jesus very happy