The traditional time for pruning pecan trees has been during the dormant season. In the photos below, you can see a before and after view of dormant pruning. Dormant pruning is
corrective pruning. Notice that almost all pruning cuts were made to correct the problem of "crows" feet. When pruning during the dormant season, you just have to hope one of the branches in the crow's foot is heading in the right direction. There appears to be a central leader in this tree but its is far from being well defined or dominate. When this tree breaks bud in the spring, a whole new crop of crows feet will develop.
In contrast, summer pruning is
directive pruning. We use our knowledge of pecan tree growth patterns to prune the tree during the growing season to direct new growth into desirable directions. Starting shortly after bud break, when new shoots are about 6 inches long, we can define the growth of the central leader with a single snip of the clippers. The photos below show the terminal of a young tree before and after summer pruning. A single pruning cut (red line marked A) removes all competing terminal shoots, directing all of the tree's energy into growing a single strong shoot that will grow straight upward and become a dominate central leader.
Don't forget the two foot rule when pruning the spring flush of new growth, . The photos below show the before and after view of the same terminal shoot pictured above. Notice that I pruned off all lateral shoots within the top 2 feet of the terminal.
I also make directive pruning cuts the the tree's lateral shoots. During the early spring flush of growth, the terminals of lateral branches will sprout several new shoots. Remove any new shoots that point upward.
When new growth on lateral branches has reached 2 feet in length tip prune the shoot to a bud that is pointing downward (photo above, right). Tip pruning lateral branches helps to change the tree limb's focus from shoot extension to radial wood growth (the limbs get thicker). Tipping also promotes dormant buds on older wood to break (photo above, right), ultimately leading to a foliage dense canopy.
I also make directive pruning cuts the the tree's lateral shoots. During the early spring flush of growth, the terminals of lateral branches will sprout several new shoots. Remove any new shoots that point upward. 
When new growth on lateral branches has reached 2 feet in length tip prune the shoot to a bud that is pointing downward (photo above, right). Tip pruning lateral branches helps to change the tree limb's focus from shoot extension to radial wood growth (the limbs get thicker). Tipping also promotes dormant buds on older wood to break (photo above, right), ultimately leading to a foliage dense canopy.