re: Pruning Crepe Myrtles

Prune for desired shape. They absolutely DO NOT need to be pruned to flower, nor is the horrible, cut-off-the-entire-crown pruning a very good idea. It leads to a weak tree that tends to split.

So look at what shape the tree is now, and think about what shape you want to achieve. Some thoughtful consideration from different viewpoints will tell you what you need to remove.