I agree with salvialady - that's a great book.
A couple of thoughts - with Peaches and Nectarines it seems there's an interesting challenge - you need to prune them hard enough to stimulate new growth each year (because the fruit really only happens on one year old wood), however th one year old would is the at the end of the branch, so if you cut out a 2 or 3 year old branch you'll undoubtedly cut out A LOT OF 1 yr. old branches.
So when you're pruning the tree you have to think "how do I keep plan for the future and
prune for this year.
A basic thought: one year old would is straight, and has NO other side branches coming out of it. Even if it's a little side shoot, that usually means that branch is more than one year old. So for fruit production you don't need those older branches anymore.
In my experience it's not that hard, i think of it as having to get to know your tree for awhile. I walk around the tree, find the tips of the tree and go backwards. I find where the one year old branches are at the tip (and along the main branches) of the tree and trace back down toward the trunk. Then I imagine what the tree would look like without that big branch, and how many of the 1 year old branches would be removed. The reason I would take out a larger older branch it to stimulate MORE NEW BRANCHES for future 1 year old wood to grow on, not just to remove them. Then I slowly remove old branches and check to see that i'm leaving enough one year old branches. I remove all of the 2 yr. or older branches THAT aren't supporting a branch.
So at the end my nectarine tree basically looks like a nice vase shaped tree with only nice "structure" branches (that define the form) and 1 yr old branches getting ready for new fruit.
One last thing - as salvialady said, the most productive part of a 1 yr. old branch is the middle third - What does that mean to you? It means you should cut off the top 1/3 off each one year old branch. I basically just cut the tip or couple of inches off and it seems to work fine.