I was applied online and was contacted by phone for some kind of pre-screening, which was a pretty informal discussion. I was then invited to attend one of ECC's recruitment seminars. This is a gruelling all-day event - for me, 09:30 to ~18:00. They don't ask much, do they?! First of all there was a very long presentation (the kind of stuff they should really be telling you after you have been offered the job) where they are watching+assessing you - make sure you ask lots of questions and take notes. There's also a meet and greet style task with the other applicants. Of course the atmosphere is strained because you're all trying to be friendly but secretly constantly wanting to get one over on the others. After the lengthy presentation, there's a grammar task, it was 75 questions long, in my opinion it was pretty easy, but some candidates were knocked out after this due to their performance on the test as well as during the presentation. There was a break for lunch and the remainder of us then had to give a teaching demo. You had to work with a partner and were given 15 minutes to prepare a 6-8 minute lesson on a given topic for a given age range. It's made very awkward by the 'students' being your fellow applicants and therefore native speakers - they key here is lots of enthusiasm, not ranting on, and making people stand up and move about. Don't try and stab your partner in the back, they're assessing your team work too. If you do well on this stage you'll then be given a 1-1 interview, which unlike previous comments indicate, is actually pretty intense, make no mistake this isn't just a casual chat. At this point I was made an informal job offer, pending agreement with Japanese HR.
All in all, this is a brutal interview process. I live close to London but fellow applicants had flown in from Edinburgh, Dublin, etc. It's long and gruelling and you have to keep up the enthusiasm and smiles (which is basically what they are are looking for) all day. If you can do that you'll probably get through. It's pretty ridiculous imo but us fresh university grads without experience don't have much choice but to suck it up.