A good ad should grab your prospects or customers attention. The headline should emphasize a call to action: what they should do. The whole ad should be written in the present tense "THE NOW" and always emphasize YOU "WHAT YOU CAN DO FOR THEM". It should be generic in nature: not promoting a specific business but more an oppurtunity. There should always be some type of phone number in the ad.
Some examples of good headlines:
"MAKE THOUSANDS OF MY REFFERALS"
"THE MAGIC OF SECRET, LITTLE RECORDED MESSAGES"
Some examples of effective words to use in an ad:
FREE, SECRET, BREAKTHROUGH, SHOCKING, DISCOVER, EXPLOSIVE, RISK-FREE, ECT., you get the idea.