Avoid swearing... Let your yes be yes and your no be no..
Matthew 5: KJV
33 "¶ Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths: {34} But I say unto you, Swear not at all; neither by heaven; for it is God’s throne: {35} Nor by the earth; for it is his footstool: neither by Jerusalem; for it is the city of the great King. {36} Neither shalt thou swear by thy head, because thou canst not make one hair white or black. {37} But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil."