When I went and farmed dailies to fill up my 25 dailies to try to kill Coren Direbrew, I noticed when i had done all 25 dailies, that I could get the same daily again.
For example:
Daily yesterday was Black Knight’s heart (hToC)
I did this daily first, then all the Argent Tournament Dailies, cooking/fishing, Quel Denas, and brewfest.
I had already turned in Black Knight’s heart for hToC, but got the quest again.
This is great for:
When you’re farming heroic achievements (say you failed Less-Rabi, and would rather go back and get 2 Triumph badges instead of just working towards the achievement)
When you really like the daily. (I love hToC, but really don’t feel the desire to do hOculus)
When you’re working for a specific item from a heroic (Tank trink off 2nd boss from hAN)
Step #1: You do the Heroic Daily.
Step #2: You do 24 other dailies.
Step #3: You turn in dailies before 3AM server reset.
Step #4: You return to Heroic Daily giver, and he has the Heroic Daily still.
Step #5: You take that daily, and do it again the 2nd day, AFTER the heroics have been reset. Your heroic ID is saved from whenever you do the daily until 9AM server.
You might think it takes less time to just do another heroic, but for someone like me, who does way too many dailies every day, it just takes a quick trip to QD (20 minutes) to finish out the rest of your dailies.(daily bg/heroic&norm/Argent/Hodir/cooking/fishing)
An alternative way is to catch the dailies right as they roll over. There’s about a minute within which you can pick up the daily from the previous day. The new day rolls, but the old quest sticks there for a minute. It’s great for when a daily like crocs in the city pops up, and you want more chances at it.