I don't clearly understand what you mean by how to tackle with the DLCs.
But anyway, as blastingcap suggested above, indeed, doing the Warden's Keep quest first is certainly a good idea, there's good exclusive items to be found during that quest and the storage chest you get from it is going to help if you don't have another one with modifications, which is my case (I have a modification that adds a storage chest in the camp, which makes things very easy to manage).
Usually, what I play first is Leliana's Song (available under the "Other Campaigns" option in the main menu), before starting Origins, since you get the Battledress of the Provocateur from completing it which is then exported to an Origins game. After that I start Origins, then I usually go for the Circle of Magi first right after I'm done with the basic Lothering clearing. I'm doing the Circle of Magi first due to the extra stats points you gain from the Fade. After the Circle of Magi then I go for the DLCs and the side-quests. As far as the DLCs are concerned I often go for Warden's Keep first since I want to get rid of that guy in the camp asking me to help him for that. Then I go for the Stone Prisoner quest (Shale), and finally I do Return to Ostagar. Once all of that is done then I resume on the "normal" quests (excluding DLCs) in any order.
In terms of play order, I would go as follows (referring to DLCs, assuming that you own all of them):
1) Leliana's Song (separate campaign)
1b) Start Origins and go with:
2) Warden's Keep (within Origins)
3) Stone Prisoner (within Origins)
4) Return to Ostagar (within Origins)
4b) Then, once Origins is completed, I'd go with The Darkspawn Chronicles (separate campaign) since it allows the player to see what would have happened had you been on the Darkspawn side, assuming that your Warden had not survived the Joining.
5) Then, after that, I'd go with The Golems of Amgarrak (separate campaign)
6) Dragon Age: Awakening (expansion pack)
7) Witch Hunt (separate campaign)
You should play Awakening and Witch Hunt last since you can export a saved game coming from Witch Hunt to play in Dragon Age 2. Technically you can import a saved game coming from Awakening itself to play your Warden in Witch Hunt, so everything you did in Awakening is kept in memory for Witch Hunt, and then everything you do in Witch Hunt is added to the flags of events (Awakenings events + Witch Hunt) for an exported game to Dragon Age 2, if you ever consider doing so.
But keep in mind that playing Witch Hunt by itself won't change much, or most likely nothing at all, the thing is that Witch Hunt is basically useless, it really adds nothing to the story and reveals nothing worthy, so just ending the whole Origins stuff with Awakening is sufficient, and then exporting your Awakening saved game over to Dragon Age 2 will be more than enough.
Hope it helps.