Whats the most important to remember from this?
For me, it's that there are many different lock systems and it's important to be prepared for the system you're going to have to negotiate.
Also, make a fenderboard out of a 2x6 about eight feet long.
I'm familiar with the Champlain and Erie Canals. Usually, you can pass a dockline behind a vertical pole in a niche on the lock wall and just ride it up or down. Or else you grab a weighted line that hangs from the top of the chamber, and pull down on it to keep your boat alongside. (wear gloves)
One of the biggest helps is knowing where in the lock chamber the water enters. Sometimes it's on the side; tie up to the opposite side to keep from getting pushed away. Sometimes turbulence from bottom-fills can push you around, too. That seems to be the biggest problem I've encountered inside locks, and you can neutralize it by avoiding the inlets.
The worst time I ever had with a lock was when the keeper cracked the gates to empty it, and I was downstream. The rush of water nearly washed me off the wall--I was single-handing and holding the line around a cleat that was just out of reach to tie to. With a heavy 33-ft cruiser it was dicey for a minute or two. Lesson--stay a good distance downstream of the gates when waiting to lock through upstream.
Otherwise, I've found them pretty easy to negotiate.