Blueberries do best with regular, annual pruning for best fruit production. Early spring, just as they start active growth, is time to prune them.
Prune by first removing all diseased and broken canes. Then remove older canes, those 7 yeard old or older (if you can tell). However, remove no more no more than three or so mature canes each year so you don't cut down too much on fruit production.