The order I remember was this, from my neighbor's draft horses and wagon -
A 2 horse hitch has a single shaft, between the horses, that turns the front wheels of the wagon when the horses change direction. The pulling power is not applied to the shaft, it's pulled by the harness traces attached to the whippletree, which in turn is connected to the front of the wagon body. (they are complicated!)
http://horsedriver.com/Glossary.aspx#harnesspartsnames
Put on harnesses (including collar, bridle, etc.)
Reins are doubled or coiled and fastened to something to keep them from dragging - I forget where, but it was probably on the horse's butt, on what would be the outside of the hitch.. The reins run through things on the harness that hold them up.
One at a time:
Lead horse in front of the wagon
Back it up
Connect the harness traces to the tree
http://en.wikipedia.org/wiki/Whippletree_(draught)
Connect the center shaft to the pole strap of the harness (the pole dangles between the horses)
Repeat for the other horse.
Collect reins and throw them onto the driver's seat of the wagon.
NOTES: A well-trained draft horse will walk over to the wagon and back right into position, waiting to be hitched.
A team has its preferred order of hitching, and a horse has its preferred side of the team (they get habits). If you try to hitch the number 2 horse first, or put Molly where Dolly ought to be, they can become very uncooperative.
4-horse teams are hitched the same way, but there is an extra set of trees for the front pair, not a longer shaft. They are even fussier about where they are hitched id they've been working together for long - the wheelers don't like being in front, and the leaders resent having to be in the back. Normally bigger horses are the wheelers and the smarter or more reliable ones are leaders.
If you get to 6 and 8-horse hitches, you need really well-trained ones. One rancher had a 8-horse hitch of Shires he used for logging, and they worked to voice command. They were big shiny black horses with very hairy white feet, that he could get prancing in unison,
