Before foraging for wild berries, purchase a good field guide that gives plenty of information on berries and provides pictures. A field guide tells you what berries grow in what location, narrowing down the possibilities.
Study the berries by looking at how they are grouped on the plant. Raspberries, blackberries, salmonberries and thimbleberries are all part of the Rubus family and are composed of little drupelets, or little fleshy pods that make up the fruit. Bilberries, huckleberries, blueberries and cranberries are all part of the Vaccinium family and are single fruits.
Look at the seeds of the berries. These range from hard nutlets to soft seeds. Blackberries contain small seeds in the fruitlets. Seeds on strawberries are located on the outside of the fruit.
As a general rule, eat only fruit that you can identify with 100 percent certainty. Some toxic berries look similar to edible berries. For instance, the pokeweed berry looks similar to a blueberry but has a shiny, glossy appearance instead of the dull, dusted appearance of a blueberry. If in doubt, do not consume.