Place in plastic freezer bags--add sugar to suit your taste ( we use about ¼ to ½ cup of sugar to every 2 cups (2 half-pints of berries). Be sure to note the quantity of berries & sugar used on the package to avoid "guesswork" when you use the raspberries later. Tie & put the bags into the freezer immediately. It is not necessary to dry out the berries if you have washed them.
Place on a cookie sheet one layer at a time in the freezer. After they are frozen (usually the next day) scoop up the berries and place in a freezer bag. If you have washed the raspberries let them dry before putting in the freezer. The main idea behind using a cookie sheet is to allow the berries to freeze individually and not clump together in one big frozen ball that is difficult to use. Avoid leaving the raspberries uncovered for more than a few days to prevent desiccation (freezer burn). These berries can then be removed individually for cereal or shortcake during the winter!
Try thawing them out half way (don't cook them) in the microwave before you use--- this will take some experimentation with settings & time to get just right. If you take them out of the freezer and allow them to thaw slowly, they will usually be soft, mushy, and not very attractive (but taste OK). Frozen raspberries can also be plopped directly into your cereal and milk and will thaw rapidly since they are hollow in the center.