Prune at the right time of year. Prune the tree back before the first springtime buds appear. Wait until fall to remove any live branches, to help the tree as it goes dormant for the winter and give it a boost in the springtime.
Remove diseased or weak branches as soon as you see them; broken limbs can cause severe trauma to the tree. Fast removal of dead branches will keep the tree strong and thriving.
Prune your sycamore tree's branches flush with the branch "collar." Cut each branch right to the notch of the original trunk to leave sufficient area for it to scar over. This is important because open wounds on the tree are easy targets for infestation, which you want to keep to a minimum.
Treat any wounds from pruning by covering the area with tar to repel pests and prevent it from drying out.