Proper pruning technique
To begin, remove any dead or diseased branches, followed by any that cross or rub against each other. Next, working from the trunk outward, remove twigs and any scrubby growth to promote good air circulation and an open framework; you should be able to see through a well-pruned Japanese maple, even when it’s in full leaf. Branches that run parallel to each other should be removed, as well as any running parallel to the main trunk. Where a bushier habit is desired, cut to just beyond a pair of buds on the twig—two side shoots will emerge.
When removing large, mature branches, be certain to make a cut flush with the branch collar—the slightly raised area where branch and trunk meet. This is where the tree will generate new bark, in effect healing the wound. Never use wound dressings or black sealing paint over cuts; far from keeping moisture and disease out, they lock them in.