Read this:
Training and Pruning Your Home Orchard
http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/22166/pnw400.pdf

Here is a link that might be useful: Training and Pruning Your Home Orchard

jean001a, that is a nice article on general pruning. I have a specific question though:

Is it too late to make a heading cut on a central leader now that it is summer?

In the absence of any advice, I'll probably just leave the tree alone and let it establish itself more. I'll prune back the leader (with this summer's growth) next winter.

Here's a pic by the way.

Hi Ed-
I will lend some experience to my 4-1 apple. Last year my 4-1 looked like this on the main scaffold of all the 4 types. It was almost like the tree was damaged somehow but the ends were just like your tree and leafed out properly. I had probably a foot of just branch with no leafing. I waited until late November and cut them back quite substantially and it leafed out properly, flowered and now has apples. So, I would probably just let it go until dormant, then cut. It worked for me. With a tree that young its really about the root development and removing 30% of the leaves can't help early summer.

ConwayOrchard, thank you for the reply. You confirm that I will just let the tree settle in this season :)