I searched the web but I couldn't find any achievement guide. Maybe I didn't search well, but I think there is no good achievement guide for new players who just want to get all the achievements done quickly. There are indeed guides for individual achievements, but there is no way to know which way to start. My guess is that you need to start by leveling 6 characters (5+1 for all-professions achievement) so I'm working on leveling my characters right now. I'm also working on making money with the AH, as I have experience in this regard and gold is a good thing to have especially for the "expensive-items" achievements.
But then I don't know what I will work on. Do you guys have any suggestion on what to do after or while leveling? Any daily quests I should be doing? Any reputations I should be farming first? Any help is appreciated.