You should prune out any dead/damaged/diseased wood. As long as the tree isn't interfering with a structure or electrical equipment, let the tree develop normally. If you need to prune the tree to reduce the size, bring the tree back in bounds, or to help improve its shape, see this Clemson HGIC fact sheet on Crape Myrtle Pruning:  http://www.clemson.edu/extension/hgic/plants/landscape/trees/hgic1009.html


According to the US Forest Services fact sheet on the Tuscarora crape myrtle (http://hort.ufl.edu/database/documents/pdf/tree_fact_sheets/lagxf.pdf), "Pruning should be done in late winter or early in the spring before growth begins because it is easier to see which branches to prune."