The main idea behind Attack & Defence Target Areas is to allow your knight to hone his skills to cause Maximum Damage to an opponent whilest receiving the Minimum Damage to himself.
As with most things like this there are a HUGE number of possible combinations for your knight and coupled with an opponents combination it is unlikely that you will ever fight someone with the exact same Attack & Defence Areas. You can however tweak this to find what works relatively good for yourself.
Hopefully this will shed a little light on this so you can experiment with a bit of an idea of what you are actually doing.
Attack Area's
The difference between attack area's is two things:
Hit Chance and Damage.
Area 1: +25% Damage, -25% Hit Chance
Area 2, 4 & 7: +10% Damage, -10% Hit Chance
Area 3 & 9: +0% Damage, +0% Hit Chance
Area 6 & 8: -10% Damage, +10% Hit Chance
Area 5: -25% Damage, +25% Hit Chance
The area that is right for your knight depends on a few things:
1.) Elemental Damage - If most of your damage is coming from elemental then it would be recommended to attack Area 5, 6 or 8 as hitting your target is the most important part to achieving Maximum damage.
2.) Weapon - If you have a high damage weapon it is generally recommended that you hit areas 1, 2, 4 or 7 as the damage multiplier is a huge bonus and will form the greatest part of your damage.
3.) Stats - If you are relatively high in Weapon Art (and therefore strike chance) compared to those around you then 1, 2, 4 or 7 are good areas. If you are not high in Weapon Art then 5, 6 & 8 are good areas.
Now you will have varying combinations of these things so it is an applied theory. Let's talk in pure Damage...
e.g.
We have a high damage weapon, little elemental damage and our stats are poor. => Recommend 3 & 9, with one possibly two in 2, 4 or 7
We have a poor weapon, but a lot of elemental damage and our stats are good. => Recommend 2, 4 & 7 with a 3 or 9
Remember the Damage bonus only applies to weapon damage NOT elemental...
Defence Area's
The difference between defence area's is the number of attack areas it cover's and the relative damage caused if unprotected.
Area 1: Areas Covered 2. Damage - HIGH
Area 2: Areas Covered 2. Damage - LOW
Area 3: Areas Covered 2. Damage - MEDIUM
Area 4: Areas Covered 4. Damage - MEDIUM
Area 5: Areas Covered 4. Damage - LOW
The area that is right for your knight depends on a couple things:
1.) Type of Damage - If you are getting lots of elemental damage then you need to cover easy to hit areas such as 4 or 5 to reduce the number of hits being taken. If you are receiving lots of physical damage then areas 1 and 3 are recommended.
2.) Stats - If your Defence Art and Aptitude are high (and therefore your Defence Chance and 'miss' ability) then defend your areas such as 4 or 5 to almost completely stop any damage being done. If your stats are low defend 1 and 3 to stop the huge damage bonuses.
Now you will notice I didnt once recommend Area 2... Most people believe this to be an ineffective area to block.
Anyways thats the basic theory behind the Attack and Defence Area's. Feel free to have a little play but remeber it costs silver everytime you change it and I recommend singular changes then a minimum of 5 attacks before making the next change to fully test the new setup.