This seemed like a better question to answer directly, so I'll try to tell you what I think I know...
If you're going for a more realistic style, the goal is primarily to show gravity acting upon the mass. Fat is soft, but in a way that is being contained within something else. That means when it hits a surface it turns up at the edge sort of like the surface tension on a water droplet. If you have a few of those droplets on top of each other, there are parts that fold in and parts that only bend in slightly to form a little dip. The bigger the person in question is the more of these dips exist on larger surfaces without rolls. Everyone had different anatomy so the rolls and the dips will form in different places, but it's good practice to look at models or different artists to try and know where those folds lie. For example, a big one that I keep forgetting is that the love handles actually frame the fold that starts the bottom of the belly. It's little things like that which can make your character feel more or less cartoony depending on what your goal is.