Always use a sharp pair of secateurs, loppers and a pruning saw
Start by removing crossing, rubbing, weak, dead, and diseased, damaged and dying branches.
Keep the centre of the tree open by removing larger branches with a sharp pruning saw. If several large branches need to be removed, spread the work over two or three winters as very hard pruning encourages even more vigorous growth.
Reduce the height and spread of any branches that have grown too large by cutting them back to a vigorous lower branch (making sure this lower branch is at least one-third of the diameter of the branch being removed.