Pruning - a specialised and subjective subject.
Methods adopted are very dependant on the outcomes required - commercial, lifestyle, environmental...
Here, for now, help us gather a few basic guides for "a small orchard".
And perhaps throw in some links to more interesting pruning methods.
Reg Lewthwaite has studied pruning and documented it:
universal principles of pruning and training fruit trees
Lorette System of summer pruning - some external links:
(2011)
The Lorette System of Pruning: marklee3.tripod.com/fruit.html
Summer Pruning of Apple Trees: aces.nmsu.edu/pubs/_h/h-312.html
Modified Lorette System: derrysorchardandnursery.ca/p5_pruning.html