Thou shalt not take the name of the Lord thy God in vain: for the Lord will not hold him guiltless that taketh His name in vain.The common interpretation of this commandment is to avoid using the name of God as a curse word. While this is definitely part of it, I think the commandment is more expansive than that.
There are people who do terrible things in the name of God. Using God's name this way is surely taking it in vain. On a more personal level, in the waters of baptism and each week when we take the Sacrament, we covenant to take upon ourselves the name of Christ. What are we doing with His name?
Another personal way I implement this commandment is in my decision to take affirmations instead of oaths. An oath is the typical "I solemnly swear that ... so help me God." An affirmation is "I solemnly affirm that ..." Oaths and affirmations have the same legal effect. I'm a notary, so I had to take an affirmation to uphold the Constitution, and when I become a lawyer, I will have to take another one.
My reasoning for this comes from the Sermon on the Mount.
Again you have heard that it was said to those of old, 'You shall not swear falsely, but shall perform to the Lord what you have sworn.'Although the text doesn't explicitly connect this command to refrain from taking oaths to the command to refrain from taking the name of God in vain, I see them as related. It seems to me that taking an oath would be an improper use of the name of God.
But I say to you, Do not take an oath at all, either by heaven, for it is the throne of God,
or by the earth, for it is his footstool, or by Jerusalem, for it is the city of the great King.
And do not take an oath by your head, for you cannot make one hair white or black.
Let what you say be simply 'Yes' or 'No'; anything more than this comes from evil.
Matthew 5:33-37 (English Standard Version)
This is supported in the Doctrine and Covenants.
Behold, I am Alpha and Omega, even Jesus Christ.While a notary, judge, or other government official has the secular authority to bind people to obligations, s/he does not have the spiritual authority to use the name of God in that situation. This is contrasted with the ordinances of the gospel, which are done in the name of Jesus Christ (or in the case of baptism, in the name of the Father, Son, and Holy Ghost) by someone who holds the priesthood, i.e. the authority to act in God's name.
Wherefore, let all men beware how they take my name in their lips—
For behold, verily I say, that many there be who are under this condemnation, who use the name of the Lord, and use it in vain, having not authority.
Doctrine and Covenants 63:60-62