Assuming you are being interviewed for the college:
The questions aren't fixed, but you can expect to be asked about Nav aids, locations of NATS units, and a series of scenarios ranging from an aircraft accident (what are your prioities i.e emergency services etc) to a series of radar returns on paper and determining which ones are likely to hit each other.
There will also be a personality questionnaire, the answers are generally Yes or No and you can't get any clarification from the interviewer, so just answer yes or no and don't elaborate!!
Then lastly theres the computer test, a series of numbers move across the screen and you have to eliminate the ones which will collide with each other whilst simultaneously solving mathematical equations.
This is the hardest test, but just stay calm and dont press numbers at random
Goood Luck