Account Manager, Planning at Mindshare
Application Advice: If you can demonstrate an understanding of a media agency and what they do I think it will give you an advantage. I feel like it is a relatively unknown part of the industry unless you are within it, so a basic understanding can only be seen as a good thing.
Also, I think culture is super important, so getting across a bit of personality will help you to stand out, rather than just being 1 of 100 identical looking applications.
Interview Advice: Again, I think there's not an assumption or expectation that you know too much about the industry or the detail, so if you can demonstrate a but of understanding that is likely to be really strong.
Don't be overly formal, the atmosphere is slightly more relaxed, and if you get to interview stage, it is as much about demonstrating that you can fit in within the culture of the company, as it is demonstrating your intelligence/capabilities. So, as hard as it is, try to relax, get your personality across, and be yourself.
Finally, tied to the above, I would avoid over-dressing, I don't think it would really be held against you, but I do think it just slightly demonstrates you don't quite understand the industry you are applying for. When I had an assessment centre for my internship, there were about 6 people out of 30 who turned up in full suits, and all 6 were in the group who didn't make it to the final interviews in the second half of the day!
Industry: Arts & Media