How do people control dog sleds?

Most sleds have a brake, and the dogs are trained to obey directional commands.

Some of the most common forms of these commands:

"Hike!" = move faster

"On by!" = continue in a straight line, ignore whatever you were looking at

"Gee!" = turn right

"Haw!" = turn left

"Easy!" = slow down

"Whoa!" = stop

"Let's go!" = start moving