Once you do find hot products, make sure to use a search engine like TypoHound that searches for misspelled listings. I've saved a ton of money because of sellers misspelling things!
Go to ebay and scroll to the bottom of the page. Click on the link "top products". Another way to find hot products is to follow what is trending on the internet and look for products related to those trends. Here is a link for trending videos on YouTube http://youtube-trends.blogspot.com/