I primarily sell on eBay since I'm built up there, but I do sell on Craigslist for certain types of items that I don't want to ship.

The best way to experiment is by trying to find and sell a few things around your home that may have some hidden value. Even parts of larger items can be worth more than the larger item sold separately. Get creative. Look up the value of what things are selling for and you may be surprised that something very random might be an easy $25+ item.

...Once you sell those, then it's time to look for more things to sell! Positive reinforcement helps the process flow naturally.