I visited no fewer than 4 units before my interview!! This might be considered excessive (as well as brown-nosing
) but there were 2 reasons;
1) Thought it would show the interviewer that I was suitably motivated
2) I wanted to be as prepared as humanly possible.
You obviously don't need to be this enthusiastic but you should visit at least 1 as they will be looking to ask you questions about what you saw when you were there...if they don't have anything to ask you,won't look too good I imagine.
As someone else suggested,try and visit a centre and tower.I found the visits really helped me to convert what I'd read into "real-life".
Good luck!!
777
P.s get the ABC of ATC by Graham Duke...very useful and quite easy to understand