This is a section containing guides and strategies for more experienced players. If you are a newbie, you'd rather like to read Beginners' guides section.

Warfare

Attrition - why your army dies.
Morale FAQ - FAQ on army's morale.
Troops' movement time - when, oh when, will they reach this province...
CRT - All you need to know about fighting
Complex Naval FAQ - why you don't want to be far from port for more than a year.
Land Support Costs - math for manually computing army support costs.

Tactics and Exploits

Tiny armies - single man armies are quite useful.
Synchronized looting - make money fast!
Stealing sieges - let your allies do the heavy lifting.
Turboannexation - use government collapse to speed world conquest.
Monthly movement - avoid unnecessary attrition via micromanagement.
AI milking - Attack. Get top dollar for peace. Repeat.
Directing retreats - you can control where a defeated army retreats to.
Military access with enemies - AI enemies are very generous!
Capturing unfortified ports with a fleet - unfortified ports + military access = warscore
Annexation ally - use the AI to take annexation BB hits.
How to get CBs - some hints on ginning up reasons for wars.
White flag tourism - explore your enemy's lands, on the cheap.
Bouncing armies - micromanage your siege forces to speed sieges or avoid attrition.

Trade and economy

Economy FAQ - Everything you wanted to know about the EU2 economic system.
Sending merchants strategies - how to send your merchants efficiently.

Other concepts

Build Capacity - How many men can you recruit from a province.
Difficulty level - how difficulty level affects the game.
How to make your game more difficult - a bunch of guides.
Forming majors - how to form majors, when starting as minors.
Manpower - research on manpower.
Population - how population works and affects the game.
Tech tables - when oh when will I be able to kill him.