I also tested at Scarborough yesterday. I thought the process was well run, for those that are curious:
When you arrive you present your invitation letter to a security guard (the man yesterday was quite nice), and you are asked to fill out Prohibitions form where you acknowledge that none of the situations described on the form apply to you. Most of these questions are related to criminal activity since you applied for citizenship.
The process starts right on time, so it's fine to arrive 15-20 minutes before your scheduled time - no need to arrive earlier.
At the scheduled time (ours was 11:50), the people that do not have to take the test because of their age are led into the interview room. The people that are there for the test are led into the testing room. The immigration officials advise that the process will take 30 minutes for those that do not need to be tested, and those that do should expect to be there for 2 hours.
The testing officials specifically tell you at the beginning of the test that you are not to disclose the questions on the test. They ask you to fill out the testing form in a few specific ways, and then test booklets are handed out. You have 30 minutes to complete the test.
Once you complete the test, you hand your booklet and form to the testing official, then go into the interview room. The interview room is a common room with approx 30 chairs and 5 desks with interview officials. The interviews are conducted in this room.
For my interview, the immigration officer asked me about some of my travel history (I have an extensive history), reviewed my passports, and discussed my job a bit with me. She did get specific and asked a few questions about a particular trip, and I went into some detail about the trip and what I do for work. The interview took about 6 minutes. Once it was over, she advised me that I had passed my test and scored 20/20, said she had no further concerns, and advised I would be hearing from them via email "in a few months". I thanked the official and then left the interview room and the building.
That was it - the whole process took me about 30 minutes from start to finish, but I was one of the first people to complete the test. They appeared to call people for the interviews in the order in which they completed the test.
To prepare, I simply studied the printed version of Discover Canada and took the Richmond Public Library tests (yourlibrary.ca/citizenshipcounts.ca). One thing I found useful was to load the Discover Canada MP3 audiobook and listen to it on my phone. I listened to it 2-3 times and I was set. If you can do a 100 question set on the RPL sites and get 100% you can feel confident about the real test.
Good luck to everyone!