In a 12 week project, hitting the ground running is more than a cliché. I implemented a Google Ventures kickoff sprint to rapid prototype (and have some fun too). The concept was pitched by week 02.
Aside from daily stand ups and weekly retros, we implemented a solid (and fun) mid cycle retro that helped refine the process, kill the lag and see where we could get leaner and meaner. When the real challenges came (pivots etc.), the team was galvonised and ready for the challenge.