Fine, reason flies out of the window here...
Dayloon, first of all you could gather a least a basic guide from
here or just ask a few questions in specific and people will be able to help.
To those flaming me (because that really is all youre doing) have you not thought about what happens if they do enjoy playing wow? What if they get to level 70 and think "Hey, lets join a guild that going to these raid instances where i can experience the challenges WoW has to offer" and then realise that the class theyve spent months working on just isnt fun any more and they'd actually rather be doing what that other class is doing?
At this point your pre-20 character is nothing like what you have now. Not everyone wants to raid but not everyone wants to stick to pvp either, how can you not see this from 2 perspectives? Personally i havent been too bothered with pvp since TBC came out as there is so much else to do, i really enjoy working with 24 other people to overcome whatever blizzard throws at us, and we're doing it pretty well being in the top10 guilds in the world.
So whats to say he doesnt want to try that? Unless someone tells you otherwise, you will only get a feel for your class role after level 20 until you are beyond level 20, the same applies for 40 60 and 70, it changes as you level.
"Hunters are and will always be a ranged damage class.Warriors are and will always be a melee class.Mages are and always will be offensive magic users." common sense alert, anyone can read that from the wow site.
My opinion is, play the class you'll be wanting to play when theres no more levelling to do. Certain classes are best at certain things, trying to hybrid will just ruin your chances of doing anything useful so why not get as much advice as possible now to save you getting a 2nd char to 70 to fix the first mistakes?