Blue flowers would indicate some variety of macrophylla or bigleaf hydrangea. Most macrophyllas bloom on old wood or growth that was produced the previous season. The number one reason these plants fail to bloom is because of damage to the overwintering flower buds, either due to cold or removal due to pruning. In zones below 7, it is recommended that these plants receive protection in winter to ensure the buds are unharmed by cold. If you do a search on this forum, you'll find various discussions on how to go about offering winter protection to encourage flowering.

If this seems like too much of a chore, there are some newer introductions, like the Endless Summer series, that bloom on both old and new wood and do not necessarily require protection to achieve flowering. I'd avoid pruning these types (any macrophylla) if at all possible, except to remove dead wood.

'Quick Fire' is a cultivar of H. paniculata and that type of hydrangea blooms on new growth. No protection is required and they can be pruned back hard in early spring if necessary.