Secondary Professions

Early in your adventures, you will have the opportunity to take on a secondary profession. Your character's appearance will continue to reflect your primary profession choice—a Monk/Warrior and a Monk/Necromancer will both look like Monks when it comes to clothing. The secondary profession is not about cosmetics—it's about choices. Secondary professions give your character access to a whole new set of attributes and skills. You will not be able to use the primary attribute for the secondary profession. Every character gets only one primary attribute, and that attribute will always be the one attached to the primary profession, as the name implies.

For example, a Ranger might choose to take on Necromancer as a secondary profession. The new Ranger/Necromancer would gain the attributes Curses, Blood Magic, and Death Magic. The primary Necromancer attribute, Soul Reaping, would be unavailable since the character already possesses Expertise, the primary Ranger attribute.

There are no set rules for how to build your two-profession character. You can divide your attribute points any way you wish, creating a versatile jack-of-all-trades or a master of a few more powerful ones. Many players opt for the latter, but the choice is yours.
Potential Profession Combos

Just as there is no right or wrong primary profession, there is no right or wrong combination of professions—every profession match up has the potential to be used in a unique way, and you have 56 different ways to put professions together. Tinker with your characters until you find the profession combos that suit your play style the best. http://www.guildwars.com/gameplay/skills/secondary/