There are quite a few threads already on this Steven, probably worth searching for them. However from my own experience (got me to Cranebank anyway), the obvious points like spelling, clarity, no smudges etc etc hold true for any application. The BA questions are possibly more in depth than most, if I were you, photocopy the form quite a few times and draft your answers a good number of times before you fill out the actual (spacing etc).
If you're anything like me (and most other guys on here), you will spend a good number of hours drafting and redrafting till you're happy. Answer the question directly and try not to put too much "background" info in your answer, get to the point. If the question says "Give an example..." then give AN example, not 2 or 3...may seem obvious but they can be that choosy. Things like Perseverance, degrees are normally good examples. Use of 'positive' language (without sounding like Superman) is also beneficial, be confident and don't be afraid to sell yourself, you have to.
Good luck with it.