There are many literature pages about this, even magical methods and bullet-proof templates. Good luck with them.
I just want to share some tips and tricks that have been proved useful to me to do it smooth and painless.
Other phases have more prestige, like the Strategy, which get most of the long winded considerations. Other need more work and sweat to be done, like development. But the scope is the most delicate: is the nexus between desirable (goals, expectactions), feasible (limitations) and the definite thing (design, development, content). So treat her right.