what is the best way to play the main story along with the dlc? like after a certain mission should i go to the pitt or do mothership zeta, just wanting opinions

I always start with Operation Anchorage the moment I step out of the vault. The DLC is not very hard and you
will probably be about level 8 once you are finished. You also get power armor training and some very nice gear.

When I can do it , I mix and match, doing a little here, then a little over there, then blowing off both and going yet over THERE.
My characters live in the world, and only advance the main quest when we want to see different kinds of enemies.

Fallout 3 -> Mothership Zeta (To get it over with) -> Operation Anchorage -> The Pitt -> Broken Steel -> Point Lookout.

That's not from least favorite to favorite, although the Pitt and PL are my two favorites. Broken Steel pretty much sums up the main quest-line (even though I hate that DLC with a burning passion), so I save it for near last.