Tree-trimming is necessary not just for aesthetics, but for very practical reasons as well. Untrimmed trees tend to have unstable branches subject to breaking in high winds or rains. This can be dangerous. An untrimmed tree with lots of old, dead wood is also more likely to suffer from diseases and insect damage. Plus, a well-trimmed tree simply looks nicer and adds to the beauty (and value) of your yard and home. As with most jobs, proper tree-trimming requires that you have a few basic tools. Having the right tool for the right job makes any job go more quickly and more easily.
Remove all dead and dying wood. Burn or discard any dead or diseased wood.
Remove all suckers growing from the roots or from the trunk of the tree -- suckers do not have true bark on them. Either break off the suckers or use your pruning shears to snip them off as close to the trunk or roots as possible.
Cut all branches growing downward or sideways through the canopy of the tree. Use your pole saw or a ladder and your hand saw to remove these branches. Cut all branches just outside of the node out of which the branch is growing at the trunk.
Step back and evaluate at the symmetry of your tree. Cut all branches that cause your tree to appear unbalanced. Burn or discard all removed wood.