Really, it all depends on how much work the takeout person has to do.
For example, a few weeks ago, I got some to-go wings from BWW, and I never get ranch or blue cheese or anything with them, so my order is basically them putting my wings in the box (which the kitchen guys do) and putting the box in the bag. I still tipped a buck or two, IIRC, because why not, but had I asked for stuff in little to-go containers, like ranch or blue cheese, where the bartender had to take time to fill them up and whatnot, I would have given her another few bucks.