Hi, It's not a silly question as some do work differently, but yes in general you need to queue.
Depending on the character you want to see depends on how early you have to be in the queue.
We arrived 10 mins early to see Merida and we were the only ones there until people saw her arrive but this was because she wasnt a scheduled meet and greet.
Those are the ones that people tend to get there really early especially for the princesses.
I would suggest getting there at least 10-15 mins before the scheduled hour then you should be first or within the first 10 in the queue. this certainly worked for us when we waited for Pooh and friends.
There are other meet and greets that arent scheduled and therefore it can be sure fluke to find them so keep a look out and think about returning the next day.
For Peter Pan, Alladin and Alice in Wonderland there is a 10-15 minute gap between each character so dont leave the queue as someone else will be coming out although you never generally know who it will be.
In the studios we foudn the queues for both Mickey and Buzz to be short as we arrived exactly on time and we were the first there!
When you see characters just walking about then it is a case of trying to get your child to the front of the crowd as generally there are no queues and the characters dont hang around too long.
hope this helps this is just our experience when we were there in Feb!
Dont forget to have your camera ready and your autograph book!