Oh, it's all such an evolution. At first, I'd wear or nurse sleeping baby while putting dd to bed. Then I'd let an older, more wakeful baby sit in her room while I read a story, put her to bed, and then dealt with him. Now, dd sits with me in his room while I put him in pjs and get him ready for bed, goes to her own room for "lights out" time for a few minutes while I nurse him down and have special time with him. If she's being a real pill about going to her room, I throw her in front of the tv. This happens maybe once every two weeks. Once I'm done with him, I tie up whatever ends I left open with her and then put her to bed.
Most nights, this is pretty easy now. Last night, she wanted to take a bath and our tub is in the basement. When I told her she needed to leave her teddy bear upstairs, which in retrospect was a battle I probably should have left alone, she yelled and cried right outside his room, leading him to wake up and not be able to go back to sleep for an hour. I put her to bed and had to go soothe him. So that sucked and I kind of didn't like her very much last night.

But normally, it's fine and we have found our groove.
Check out Galley for food on nights you don't want to cook.