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Overcoming objections is an important part of any copy you write. While some objections may be obvious, others are not.
Online forums are a good place to start. Find the ones that cover your product, the more specific the better, and join the group anonymously. Ideally spend a week or so commenting on other posts to build up some credibility. Then simply post something like this "Heard good things about XYZ Product. Does anyone have any thoughts that may help my decision to buy?"
The negative responses will help you identify the hidden objections that you will need to overcome.
In the early days of the Internet, one of our clients had, what I thought at the time was, a great idea. He published a specialist book and got a mate to post on several forums "Lent one of my favourite books on SUBJECT to a friend who has lost it. Can't find the publisher of TITLE and wondered if anyone else on this forum could help me track them down."
If he had no reply he then got another mate to post his address and contact details. In those days forum users tended to be fanatics who not only spotted the crafty ploy but posted death threats to him!
Don't think you'll get any death threats for looking for objections!