There's an app called "Vegan Pocket: Is it Vegan" where you can scan the bar code of a product to see if it's vegan. Some foods also will have a certified vegan label. There are probably other resources out there as well!
Food packaging ingredients
As I approach my 1/1/18 conversion from vegetarian to vegan, food ingredients baffle me as to whether or not they are free of vegan concern. Seemingly innocent cereal ingredients (nutrients) can be an eye opener. For example: A national supermarket has its own house brand equivalent of rice crispies. One ingredient listed on the box is cholecalciferol (vitamin D3). Sounds innocent. However, upon research it is found 'to be produced by the ultraviolet irradiation of 7-dehydrocholesterol extracted from lanolin found in sheep's wool'. SHEEP's WOOL?!?! One would need degrees in biology and chemistry to undertstand all this. So, how do vegans know they're vegans? Where's the proverbial line in the sand? This is sooooo confusing to a wannabe!