Use fresh blueberries that are completely dry when you pop them in the freezer. Don’t worry about rinsing the berries before you freeze them; simply place them in resealable plastic bags or their original containers, and store on your freezer shelf.
If you prefer to rinse the blueberries first, dry them well with paper towels, then transfer them to freezer containers or resealable plastic bags for freezing. The blueberries will freeze individually so you can remove just the portion you need.
If you didn’t wash your blueberries before freezing them, rinse them just before use.
For best results, toss your home-frozen blueberries into oatmeal, yogurt, smoothies, shakes or sauces within 10 months.

Source: U.S. Highbush Blueberry Council