Nothing required. For extension you'll need to pop to the local immigration office wherever you're staying. It's a same-day thing usually, might need to pick up next day. Go a couple of days early. The application for extra 30 days requires passport picture and copies of passport (all pages)..
sorry Tod just to clarify here. Is there any 'limit' or funny business at the port of entry when arriving by air. Your above comment suggests one is permitted two 'bounces' (by land) /year, but airport don't count.
Secondly, thanks for making clear the land border rule runs thought the calendar year.