1. The wall lvl always gives a bonus to either the defending team or the attacking team (it only gives a bonus to the defending team if the wall lvl isn't high enough).
Therefor it's handy to be upgrading the wall at every lvl you upgrade your town hall too.
The bonus is: 1lvl town hall, lvl 1 wall = 10% bonus....
lvl 2 town hall, lvl 1 wall = 7% bonus
lvl 2 town hall and lvl 2 wall = 20% bonus....
but for example if you have a lvl 12 town hall and a lvl 2 wall then the bonus is -4% which gives the bonus to the attacking team.
(hope you understand that tip...it's a very hard one to discribe as well as understand).
Tip:
1. Make sure to use the alliance circulate message a lot...for example to tell you have been attacked, or trade, or wanting to know some things.
Tip:
Make sure to keep your citizens happy because if they become angry your losing citizens. and trust me...that ain't fun.