Our earlier post on AD is over a year old now! ..and its get a bit tired, and in need of an update given all the changes that have been introduced since then. ..and here it is!
All in all a similar amount of daily AD per character is available. It does seem a bit harder to get to today than it was last time we covered this topic. Some of the old habits were downgraded and more hoops were added. There isn't 1 way to make quick AD with little work, and if you've found one take advantage of it as its lifetime will almost certainly be short.
In the range of 40k AD per day on a level 70 character is doable by a casual player in a reasonable time. Greater sums are available depending on the amount of organization, time, and work you want to dedicate to it.
The old post is left up for historical accuracy. The parts that no longer apply wont appear here.
Daily dungeons and Skirmishes (Major change for 12b)
Weeklies - do weekly quests for 4500 AD each.
Fair warning: It cannot be stressed enough how expensive and frustrating this is to qualify for.
Having alt characters can help multiply your daily income. You get 3 character slots to start with, may as well take advantage.
See here for a more detailed look.
Fishing, Treasure hunting, and HEs in MOD 10, 10.5, 12 content-