First, a little about me. That way you can understand that the application is not all about your English skill :) All these things I put in my application.
I have a Bachelor or Science in Computer Science (New Zealand). I have had experience travelling overseas. In particular, I've been to India and helped in orphanages with a mission group. I helped in my church's kids programme by looking after about 100 kids. I've done Karate and Juijitsu. I love adventure, outdoors, and that sort of stuff.
From my interview I felt they were looking for people that had the endurance to hang in there despite difficulties. In fact, many of the questions during the interview directly addressed how I would handle in the event of the housing being below-par and that fact there aren't many churches in Japan. I told them that it couldn't be worse than the conditions in India, and that I would find a church (which I have). They don't want anyone bailing out because it cost so much to send another ALT here!
In my opinion, your character is very important to get across in the application. In fact, I didn't feel that my English was up to par (as maybe evident), but I made it here :) I'll list the things that I think are important to get across for your application:
- Firstly, you have some skill in using English (supported by something)
- Choose your referees carefully. Get across things such as work experience, clubs, voluntary projects, etc. I had a reference from the voluntary organisation I worked with, my church's kids pastor, and from place I was working at the time.
- Get across you personality and qualities of perseverance ;)
- Talk about your free time activities, clubs, hobbies, etc.
Ok, that's the ones I want to highlight the most. I could go over all the basic ones, but they ask you directly in the application anyway. I just want to get across that it isn't all about your English skill. Your English skill is important, but just don't forget all the other aspects. If you make it to the interview stage they might do a little quiz on English, but they'll also try and assess your character with different questions.
Anyway, that's enough. Everyone has something to offer, no matter your personality. Find out what that is and sell it to them on the way :)