Word of caution on those interview prep courses...
Up north, Air Canada was running interviews non-stop for a good while. One company offered an AC prep interview course. Some people really liked it and swore by it. But after a while, the folks at AC began to get frustrated because they noticed people were giving the same type of "canned" answers. When I did my interview, the interviewers asked me about my weakness, then they said "and don't say____, everyone is giving us that answer". Even in the interview-invite email they put out a disclaimer saying "please do not sign up for the XXX interview prep course...."
If you're gonna talk about a negative, follow up with how you're changing it. For example, for my weakness, I talked about how I sometimes have difficulty keeping things simple. I gave an example of how during my university I had trouble keeping my essays within the word limit and how during my instructor course my instructor always told me my lesson plans were way too long. I followed up with how I was currently working on improving this by working on the side at my old flight school and improving my teaching skills. I added that I really want to join the training/CRM department down the road as well.