Normally when going to flea markets and garage sales I've got a fairly one tracked mind and I'm hunging for good but cheap sports gear like golf clubs, hockey equipment and you name it and more importantly collector's items and sports memorabilia. You never know what you find when people are trying to sell off their junk and when you know things like Honus Wagner baseball cards could be sitting in a box, your mouth starts to water a bit at the possibility of scoring something ridiculous and outrageous.
Normally I don't pay much attention to things like jewelery boxes as I thought they were typically filled with junk but to my surprised I found some used diamond rings in one box and I s*** my pants once I had them diamonds appraised. I only started to do this after one of my friends told me he scored some nice money himself doing the same thing. Now I have more things to look at when I hit any flea markets but I find the biggest value lies in garage sales. People at flea markets usually have a better idea of what they are selling so it's tougher to find high value items for cheap. Typically they price out all of their items and some of them know how to sell a product and are tougher to bargain with.
If you hit garage sales you can find all sorts of good things and of course junk too.
So if it looks like gold or diamonds and you can pick it up for cheap then it might be worth the small investment if you are fast and good at getting jewelery appraised.