In deference to any rules about other sites, I won't post a link, but you can go to "The Dirt Doctor" and you'll find a great deal of information about the care and upkeep of trees. Trimming back is a vague term. With trees, you normally want to enhance the natural structure of the tree, pruning out crossing limbs, crowded limbs, etc., if a tree need bolts and cables, the tree is probably past saving, and whatever you put into it is delaying the inevitable. Proper pruning and trimming takes into account the "growth ring" of each branch and the trunk and allows the tree to heal itself by growing over the wound with its own bark. If an "arborist" comes near your tree with that black paint stuff, run him off and try again.
I really suggest you do some reading. I've used commercial guys, but supervised their actions and showed them how I wanted limbs cut. Properly done, trimming is good for the tree and its appearance. Getting to "proper" is not really that hard , either.
Good luck,
Jeff B.