I noticed that there wasnt any information about addons or UI in these forums so ill just do something myself.
First thing you should do is go and read the Addon FAQ.
http://www.warhammeralliance.com/forums/showthread.php?t=67885After you have done things in there you need some addons of course.

You can find some here.
http://war.curse.com/downloads/war-addons/default.aspxFew addons that i use/recommend:LibSlash
http://war.curse.com/downloads/war-addons/details/libslash.aspxA basic library for registering slash commands in the WAR interface. Needed by most AddOns.
Mostly Harmless Item Linker
http://war.curse.com/downloads/war-addons/details/itemlinker.aspxAllows you to link item stats to chat. If you control - right - click on an item in your inventory or character window it will give a brief desc and some stats of an item over the LAST CHANNEL YOU TALKED IN.
Moth
http://war.curse.com/downloads/war-addons/details/moth.aspxMoth is a mouse over target hover tooltip replacement for Warhammer's default Mouse Over Target window.
Just plain useful thing to have.
QuickSwap
http://war.curse.com/downloads/war-addons/details/quickswap.aspxQuickSwap is an addon for cycling between weapon sets. You can save your own sets and swap between them with one click.
CleanUnitFrames
http://war.curse.com/downloads/war-addons/details/cleanunitframes.aspxCleanUnitFrames is a replacement for the standard EA unit frames for WAR. It attempts to provide the useful data in a streamlined format, while getting rid of some of the "fluff" or other annoying things in the default UI.
AutoLoot
http://war.curse.com/downloads/war-addons/details/autoloot.aspxAutomatically uses 'Loot All' when looting a corpse, even when the modifier key is not held. No need to hold shift down anymore.

Well thats it for now. Hope someone gets some help from this.