Multiclassing

Multiclassing
In DDO you may play a character belonging to many classes at the same time. This is called multiclassing. You first create your character as a single class. Later, when you obtain enough experience to make a level you may pick a level in another class. You may have a maximum of 3 classes on a single character.

Multiclassing in DDO
Some aspects of DDO differ from pen and paper DnD and this is one area that has been the subject of considerable debate. The reasons for multiclassing in PnP are many, but you may find that some of those reasons are lacking in DDO. For instance while in PnP I usually play a rogue/wizard I find that in DDO many of the 2 classes abilities to support one another are missing.

What's more, in DDO it seems much more obvious that a level 10 character that has 5 levels of rogue and 5 levels of wizard is not really up to par with the other level 10's in the party. While taking one or two levels of another class at some point may offer some advantages on the whole unless the two classes really work well together (read rogue/ranger) it's probably best not to split your character evenly as in previous editions of DnD.

On the whole, while I personnaly like the idea of multiclassing from the standpoint of diversification for your character I find that if your party is properly balanced then its usually best to specialize in a single set of skills and let your comrades watch your back on things you've no skill for. -Gugran

Skill Points and Multiclassing
Max Ranks: If a skill is a class skill for any of your classes, then you can have (character level + 3) ranks in it.

Cost: If a skill is a class skill for the class you are gaining a level in, each rank costs 1 skill point. If the skill is a cross-class skill for the class you are gaining a level in (but a class skill for one of your other classes), each rank costs 2 skill point.

Enhancements
DDO adds another avenue of character advancement, the four enhancements. The less useful enhancements open to multiclassers gives another large drawback to that kind of build, multiclass enhancements.