Planning
Day 53
No matter how well you plan, you can't account for everything. In general though, planning earlier and more often in small chunks works better than all at once.
In my current project we missed a lot of small setup steps that have really added up. LESS file compilation, localization applications, proxies to avoid CORS, etc. A lot of these are easier near the beginning before the changes add up, but they are NOT free and don't forget about them!