A really good way to sell a product effectively is to understand what others think about it and the way you are promoting it. Whether that be positioning, colour, price ETC. The best way to do this would be to submit a survay on a dedicated survaying website.
I'd highly recommend this one(AWSurveys.com) where you can either add survays of your own to get information or complete others survays and earn upto $15 dollars per one!!
Its really really good for making money!
Also, while you're there the information you get will really help develop your marketing plan. For example, if people say they don't like something... CHANGE IT!
Im only posting this because the site has already made me alot of money and improved my website LOADS for literally nothing. Im in love Daniweb! :)
Hope this all helps,
Feel free to get in touch if you need any more advice at my website reecesplace.co.uk