To find good products to sell you need to keep up with the trends.
Search the net, look in the 'lifestyle / entertainment' sections of newspapers, talk to people.
Also the best and easiest products to sell are those that 'solve a problem' . And sometimes selling online is not always the best way to go. If you're serious about selling you need to be versatile.
For instance. I recently bought 400 of those shaking flashlights. Why? It was camping seasons and the flashlights solved a major problem... batteries, the lights never need batteries. Now i looked on ebay and you can buy them for next to nothing, actually less than i paid for them in some cases.
So what i did was go to local flea markets. (Never pictured myself selling at flea markets) It was a new experience for me!
But after only 2 days of going to the flea market I sold out! Sold them for $10 each and made a 400% profit!
The key is to be versatile.