The "head" is called krausen, and it will fall when fermentation is finished, leaving a ring of crud around where that head was. Airlock activity and krausen are pretty fair indicators of fermentation happening but the only way to know when it's finished is to use your hydrometer. When the sg falls around 75% or so, it's ok to move to secondary (the clearing tank). When in doubt, it's better to leave it longer. After the main fermentation is over, the yeast are still busy cleaning up after themselves, eating up their waste products so it's always good to let it finish up completely before moving it.
I usually use the 1-2-3 method- 1 week (or more) primary, 2 weeks clearing tank (secondary) and 3 weeks in the bottles. When I dry hop, that schedule changes some. I usually rack from primary after about 10 days, and then leave it sit for a little while. Then I do my dryhopping anywhere from 3-7 days depending on what I'm going for.
I've never done NB kits, but I assume they came with good instructions for their particular kit so that's a good place to start.
