Balancing Your Primary and Secondary Class
In order to do well in PvP and PvE in Guild Wars, a careful balance must be struck between your character’s primary and secondary classes. The skills your character uses are directly related to your primary and secondary class, putting a great deal of emphasis on what classes you choose.
Some people choose not to take a secondary class. I have found that the secondary class can only help your character. You are no worse off having 80 extra spells. On the other hand, if you choose not to take a secondary class, there might be a specific instance (probably more than once) where one skill from a secondary class would have benefited you. I would highly suggest taking a secondary class. You aren’t locked into it and can change it later in the game if you so choose.
The real question is how should you balance the two classes? Should you have equal parts primary/secondary in your skill bar? Should you only use one or two skills form your secondary. The primary factor is the purpose of your character. Make sure you choose a primary class whose primary attribute (an attribute you get only if you play this class as a primary, not as a secondary) supports what you are trying to accomplish. This is the number one factor as far as the types of skills you choose from each class. If you are an Elementalist/Mesmer focusing on high damage output, using Mesmer inspiration spells will do you little good. Domination magic would probably be your best bet with a damage based character described above.
Keep in mind, that your secondary class should also support the central focus of the character. For example if you plan on playing a Ranger that focuses on marksmanship and beast mastery, choosing to be a secondary monk that focuses on protection prayers is not a good choice.
It’s always best to have a purpose for your character and stick with it. Don’t spread yourself too thin. Because the game centers on grouping, players who specialize in one area are rewarded. By grouping together with others of different specializations, you cover all the aspects needed for a successful combat group. Being mediocre in many areas is never as good as being strong in one area. The purpose can be as general as damage output or tanking or can be as specific as anti-caster or elemental defense. The important part is sticking to it. With that in mind, put points in attributes and use skills that support your primary purpose. Whether your secondary provides one "must have" skill or many helpful skills, as long as you specialize in one area and balcne your classes accordingly, you will be much more successful in the long run.
Lectalist Firehands
this might be of a bit of help