How to Prune a Tree
It is difficult to give advice on pruning, there are so many variables.
Trees are much like people. When their small they are like a child, everyone likes them. When they're in their teens you form an opinion. When their adult you either like them or you cut them down.
Native trees such as the ones that we grow and sell are however relatively easier to prune than most. Using sharp clean tools lesions disease.
I personally always look for, as in life, everything requires balance. So I do this with my trees.
In the early stages all you need are secateurs. Stand back and look at your trees, each one is different, so treat them as individuals. As the tree grows remove lower branches making clean cuts close to the trees trunk. This helps to get the mower underneath and encourages rapid growth. Look for forks in the trees. A decision has to be made as to which one will be removed. If allowed to grow one may split away from the tree and disease may occur. Usually one will be stronger looking from the other but before you precede again look for balance. If you feel that the one you want to keep may be a problem later on call in an arborist for professional advice.
Some tree experts recommend not topping a tree but if you feel its tall enough, why not cut out the central leader. This is called Pollarding. I have seen a great many trees done this way and they look great. They tend to broaden though and give a lot more shelter if that is the look you're looking for.
Broken limbs should be sawn cut well back from the break in case of disease presence and painted with a tree wound dressing.
Pruning when a tree is say three to four meters high. (Specimen pruning). This is the time that you can really make an impact on the shape and how you envisage the tree to look in ten years time. You can have an influence on what it will look like by pruning branches that you believe are going the wrong way. Remember it's all about balance. This method is called Coppicing. Use the tree wound dressing when you decide to do this and prune only in early summer. This lesion the likely hood of disease. Sap flow is high in summer months. Don't be too concerned if it is excessive, the dressing will protect your tree from disease.
There are many books on this subject that go into depth. If you have a lot of trees, at about the three year mark call a good arborist for onsite advice, it will be well worth it.
Trees are an investment and boost property value.