In past years, our team has put 2 mechanical switches on the robot, and for every configuration of the switch (ON ON, ON OFF, OFF ON, OFF OFF), you could have a different autonomous code. All you had to do was put the code in an if statement and write a notecard out to the drivers explaining what flipping the switches would do for the autonomous. You could have as many as you wanted, but 4 seemed to be the magic number for us. This method worked the best when we didn't have any programmers, but a team full of mechanical kinds of people.
However, we've been experimenting in recent years with the SmartDashboard, and if you want a more updated method, picking straight from there is the way to go.
