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 increases the spammability of ranger skills and certain other profession's skills by decreasing the energy cost. Expertise skills are used to enhance other skills and have an all round selection of skills.

Expertise reduces the energy cost for the following types of skills:
 * All Ranger skills
 * Attack skills
 * Binding Rituals
 * Touch skills

No other types of skills are affected.

Skill cost modification by expertise
Red text means the skill has gone down in cost this level.

Alternate skill cost chart
Using this table

All 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!