Typically we will make a
rules test, and also conduct
interviews.
Once people have taken those we make a short list for round 2, typically 50-75% of applicants, based on their scores and interviews for each position. They do a general skills test for their chosen positions.
For drivers that is pretty game specific, if it's an open field then there will be high speed control and defense tests, if it's crowded there will be lots of tight driving in spaces.
Manipulators are paired up with mentors or students who are experienced at driving and then coached and judged based on their response time and ability to communicate and follow directions.
Human players are given a sort of skills challenge. For example this year it was three different challenges. The first was rolling boulders on command, then rolling boulders so that they would get to a certain spot by x number of seconds. (I would say 12 seconds, and they would have to wait until they were ready to throw it, etc.)
Finally 3 or so students are selected for each of the drive team positions for final selection. All of these students have the skills and personality to make it on the right drive team. They are paired up and have to work together to control the robot (usually a prototype robot or a previous robot) through specific tasks. From this the best group is picked based on chemistry and skills. A fair balance of skills on the robot is also considered but is not a decision driver.