“To fulfill all the words of this Torah, which are written in this scroll, to fear this glorious and awesome name, the Lord, your G-d” (Deuteronomy 28:58).

It is forbidden to say G-d's name, unless it is in the context of a blessing, prayer, or some other form of praising G-d.

– When practicing a prayer or blessing, G-d’s names should be omitted. Alternatively, the word “Hashem” (which literally means, “The Name”), is often substituted for G-d’s name.
A parent or teacher may have the children practice prayers or blessings including G-d’s name. In fact, the educator, too, may utter G-d’s name when instructing the children how to say a particular blessing, in order not to confuse the children. [Once again we see the importance of education. G-d allows His holy name to be said “in vain,” for the purpose of educating Jewish children!] 

– This prohibition applies to all languages. It is therefore improper to exclaim “Oh G-d,” or “My G-d!” However, it is permitted, and encouraged, to say “thank G-d,” “G-d willing,” or “with G-d’s help...” Such statements are not considered uttering G-d’s name in vain; to the contrary, they are glorifications of His name.

– One should not utter G-d’s name when in a bathroom, shower house, or when naked.

– One who is reading verses from the Torah may say the names of G-d’s which appear in the text.

– One who inadvertently says G-d’s name in vain – for example, if one mistakenly recites a blessing, or recites a wrong blessing – should immediately say the Baruch Shem (“Blessed be the name of the glory of His kingdom forever and ever).