Shaping the Bush

It will help if you have a mental picture of what you are striving for in post-pruning shape.  Ideally, modern rosebushes should form a classic urn shape, with canes radiating from the bud union, arching outward and upward around a free center.  Opening the center of a bush is advised not only for appearance, but also for the more important reason that light must reach interior growth as part of the metabolic process for chlorophyll production.  Also, a bush free of growth in its center has better interior air circulation which helps prevent diseases such as mildew.  Blooms appearing in the center of the bush are often wasted anyway, because they end up being deformed or badly damaged from rubbing against other unwanted growth.

Shaping bushes may not seem so important for you right at first.  It will become so as your bushes grow and mature.  Many modern roses are vigorous growers, and they have to be kept within bounds if landscaping is a consideration.  No matter what constraints you have, shaping at pruning time must be carried out with an eye toward the future, since you are creating the framework for all of next year's growth.