[CatOne]

OmniFocus uses contexts for a lot of that stuff. You can define projects as linear (forget the name), parallel, or single-action lists (basically, buckets). For the first two kinds of projects, if you set a filter on "next action" it will show you only the next action.

There's good documentation for the Mac version of OF on Omni's site, as well as a "Doing GTD with OmniFocus" white paper on their site. They both are mostly focused toward the Mac version, but the concepts should carry over to the iOS version(s). I suggest you read them, as OmniFocus can be pretty obtuse at first. I've never really warmed to it, despite 4 years of use.