Skill Tips:....

Skill Tips:
Most skills have an Energy cost. Keep track of how much Energy a skill requires and how much you have readily available, especially if your character uses magic often.
Active skills are fully lit. Darkened skills are temporarily inactive and require either recharge time or adrenaline in order to utilize.
Some skills—particularly those associated with the Warrior profession—require adrenaline and will recharge automatically during combat because you build up adrenaline during the fight. Adrenaline is a bit like Energy, except you do not have a bar with which to track it. To check on your current adrenaline levels, just check an adrenaline-based skill on the skill bar. When it is brightly lit, the adrenal skill is ready to use.
Some skills require a particular weapon type, such as a sword, axe, or bow. If a skill reads "Sword Attack," you cannot use that skill while wielding any other kind of weapon.
While outside of town, you can rearrange the order of skills on your Skill Bar to your heart's content, although you cannot equip different skills until you return to an outpost.
Signet skills do not cost energy to use, but usually take time to activate—time during which you can be interrupted or hit. Use cautiously!
Certain types of Assassin attacks require an exact sequence, otherwise they will fail. Available Assassin attacks will light up. http://www.guildwars.com/gameplay/combat/skillbar/