Everyone seem's to think a tree or shrub need's to be pruned regularly but that is not true. No pruning is done in nature though sometimes a dead branch will break off there are many form's of cultivation you can encourage growth or flowering.
A good example is the bush rose which can flower all summer long.
To rejuvenate a bush rose we cut back hard otherwise flowering will decrease within a few years time the rose will become bare at the base.
Cutting back hard can be very functional but it is an artificial measure example clipping hedge's, training shrub's and tree's.
Take a good look at the tree or shrub before you start so you don't spoil the natural shape.
Tool's need to be sharp and effective be kept rust free a tree saw is essential for removing thick branch's such as large toothed saw make's sawing live wood much easier.
To prevent splitting branch's always saw the first cut on the underside after that branch is sawn off on the upper side
or one of the side's. Try to keep the wound's as smooth as possible as it will prevent infection.