In our earlier post about Conqueror Shards it was mentioned that hints for building up AD would be given. Here are common strategies for gaining it. Mix and match them into your daily play routine and you'll build up additional AD. Some are sure things, others are risky as noted.
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.
Edit: Since posting MOD 10.5 has dropped, and new sources of income have surfaced. Added in italics below.
Daily dungeons and Skirmishes (No quests needed for these any more.)