From today (January 28, 2008) until February 19, 2008, Mercury will be in retrograde. What does this mean to you and to magic? Everything.
Mercury is the planet of communications. When it travels backwards (retrograde), everything via communications; email, spoken word, letters, contracts, computers, phones, faxes gets garbled. What you say or right isn’t what other people (including the universe) may hear.
So it is in your best interest to refrain from magic during this time. But if you must cast – make sure your words & actions are very specific – leave nothing open to interpretation.