I have been playing FO3 for quite a while now...but I just started the DLC's. I just started Broken Steel. I had Dogmeat as a companion at the end of Take it Back...and when Broken Steel started, he vanished. Do you lose h im in Broken Steel? Do you have to go find him again? I don't understand where he went? Can anyone help please?

Same thing happened to me, just wait for a meteor to fall on him and fir him to die and respawn. (Assuming you have Puppies! Perk.)

I DO have the puppies perk. But I have already wandered around a bit, went back to Vault 101 entrance, and still have yet to locate Dogmeat since starting Broken Steel. Is he somewhere back at the Citadel, or should I start Broken Steel over again and see what happens? It's aggravating me because for me he was a strong character and never died during the regular game, and I came to rely on his growling to let me know something was there.

Your companions (including Dogmeat) are supposed to be waiting for you at the Citadel, in the same room where you wake up. You have to talk to them to get them to follow you again. If they're not there, try reloading an earlier save and see if they show up.

Well when captured by the Enclave they all go back to there fired point.

Dog meat goes to Vault 101.