Now, on the Hippedown Server, starting at level 10, you can take a second class. You don't have to, and you can do so at a later level if you want (unless I can think of a reason why that would cause problems). I'm going to call it 'bonus class' for now, just because 'second class' implies the wrong kind of thing.
To do that, you have to go to Noob Peninsula. City Hall has a list of the classes available to you, and you can pick one and experiment with it for a bit. You can't level up in Noob Peninsula. If you get enough xp to reach level 11 (or so) you get a message saying so, but you can stay there indefinitely. You don't gain extra xp, though - when you level up, you'll be at 0% of the way to level 12.
Thinking about it, there's a bit of a problem. It's not an issue to have character creation take a while (and Noob Island is essentially a character creation/tutorial step). The early levels generally should go by fairly quickly. The problem is that the Noob Peninsula experience should not take much longer than going from level 9 to 10, but it should also take long enough for you to have a clear idea which of the dozen or so choices you'd want, and some of the choices for a bonus class are a lot more subtle than for a first class. If you only get four points to play around with, will you really be able to tell the difference between a fighter/gladiator and a fighter/crusader?
The best ideas I can come up with are:
a) Since there's not much pre-game and you start out playing your class as it's intended, there's no reason why the early levels have to be fast.
b) Delay the bonus class until level 15 or 20.
c) Give the character, say, 40 temporary skill points so they can see how things will develop. I don't like taking things away, though. It doesn't seem like a good idea for a temporary power-up.
d) Give the character 20 permanent skill points upon entering Noob Peninsula (even if you choose not to take a bonus class). Let's say you get 3 points per level for levels 1-10, and 4 points per level thereafter, so it's less overwhelming.