Expertise

The Expertise attribute reflects a Ranger's skill when using certain skills. This is a primary attribute and may not be used by secondary rangers.

Guild Wars description

 * "For each rank of Expertise, the Energy cost of all of your attacks, Rituals, touch skills, and Rangers skills are decreased by 4%. Several skills, especially those related to Energy costs and skill recharge times, become more effective with higher Expertise."

General description
The Expertise attribute decreases the energy costs of all Ranger skills and certain types of skills from any profession, thereby allowing rangers to spam skills without the need to micromanage energy. Skills within the discipline enhance or improve skills and other actions taken by the Ranger.

Expertise energy cost reduction applies to four types of skills:
 * Every Ranger skills
 * Attack skills from any profession
 * Binding Rituals from any profession
 * All Touch skills

Skill cost modification by expertise
Red text means that skill cost has dropped relative to the previous rank.

Skill costs by base requirements
Using this table

Most skills in Guild Wars have a base cost of either 5, 10, 15 or 25. For a specific skill, find the row with its base cost and use that row to determine how putting points in Expertise would affect its actual cost.

Note: The values in the table are exact! For example, the cost for 5 and 10  skills does not change between 4 and 6 Expertise. Don't waste your attribute points on Expertise that doesn't help your frequently used skills!