Be knowledgeable about the idea/thing you are selling.
Understand your audience.
Support your opinion with evidence.
Anticipate arguments against your opinion.
Find common ground with your audience.
This As Seen on TV product has made millions of dollars. Probably a market analysis showed evidence of potential consumers.
The commercial appeals to a certain type of person with several benefit claims.
In your notes, jot down types of CONSUMERS and CLAIMED BENEFITS. How many do you note?
Next, determine your opinion and find supporting evidence.