Blueberries should be pruned during the winter while the bushes are dormant.

Proper training of blueberries is essential to maintain plant size, shape, and productivity. In the first two years, it is important to train young blueberry bushes to promote the proper structure of the plant for maximum fruit production. When the blueberries mature, their vegetative canes require annual maintenance.

The inportant details are:
All diseased and broken canes should be removed first.

No more than two to three mature canes should be removed each year to avoid pruning out too many fruit buds.

The bush should be: a) narrow at base, b) open in the center, and c) free of vegetative clutter.

For details on blueberry production, refer to OSU Extension Fact Sheet HYG-1422-98, "Growing Blueberries in the Home Garden"
(ohioline.osu.edu/hyg-fact/1000/1422.html).

Here is a link that might be useful: Ohio State University Extension Fact Sheet -- Pruning Blueberries in the Home Garden