Tree propagate heavily when they think they are going to die...So if you want fruit, you prune them far harsher than you would ever do to a nice ornamental tree. This means you have to make a decision, do I want a pretty tree...or a fruitful tree.
You can have both to some extent, prune the tree but keep a nice canopy and you'll get some fruit which is often all the Homeowner was really wanting.
For real fruit harvest you will need to do some things that seem very drastic.
I am going to give you some of the better educational links that I feel will help you understand and be able to apply the fastest. However, keep in mind that the trees don't read, so they usually don't look like the text book :), which means you need to be focused on the WHY you make a cut to really be able to feel confident in the field.
Links to get started:
http://cesonoma.ucanr.edu/files/27164.pdf
https://www.youtube.com/watch?v=v8p6MV04irM
http://www.ext.colostate.edu/pubs/Garden/07003.html
