Each manufacturer usually has its own “code.” If you find a manufacturer whose chocolates you enjoy, get to know their codes. A swirl with two loops on it may mean caramel for one company and buttercream for another, but it will generally always mean the same thing within a brand.
Beyond codes, look for signs of nuts (large bumpy surfaces) or coconut (small bumpy surfaces). Hard caramels are typically square or rectangular and soft caramels are typically flat and round. Chocolates that are wrapped often have liquid or softer centers (cherry cordials, for example).
Some manufacturers provide maps to their treats on the inside lid of the box or color pictures to help you identify what you’re about to enjoy. But, of course, the best way to find out what’s inside of your chocolate is to taste it!