WARNING: This has only been tested on EU-Realms!
Many of us got everything (except the crocs) from the fishing daily and are only waiting for "Crocs in the City" to appear. But only a few knew this little trick. (Or call it bug, whatever you want...)
Winter:
The daily-counter get reseted at 3:00 AM. But the quests change some seconds later. If you accept the fishing daily 1 second after the counter reset, you'll be able to do yesterdays daily a second time! If you're very fast (deactivate your addons to log in faster), you can do this with 2 chars on the same account.
This works also with the dungeon dailys and the PvP daily in Shattrath. I tested this once in Dalaran with the cooking daily, but it did not work. Maybe I was too slow? Don't know. I will test it sometime later, but crocs in the city is priority #1.
Summer:
This will be a litte bit different. Quests change at 3:00 AM. But the counter is reseted at 4:00 AM. So you can get the quest at 3 AM, complete it and do it again at 4 AM.