Far be it from me to fully comprehend why any DM would start a module without first adding some color to the adventure beforehand. As for our GDQ1-7 campaign, beginning on January 6th, there's plenty of color in the Benchleydale realm, in which the hill giant fortress is situated.
Benchleydale is governed by the good king Asiago. His royal subjects are loyal to their king, and the people have lived in peace for many years...until now. The hill giants have begun to run amok, laying waste to the surrounding townships, and becoming increasingly militant. A refugee camp has taken shape, and the people no longer enjoy the protection of their regent, as they once did.
There was only one thing left for the king to do. Recruit a hit squad, send them on a (perilous) mission to infiltrate the hill giant fortress, exterminate the giants if they must, find out why the giants are running amok, and report back to the king.
A map of the Benchelydale realm will be given to the players, when they first embark upon their journey. It is five days' travel on horseback, from the southwesterly king's castle to the northeasterly hill giant fortress. Many opportunities will present themselves along the way, for the party to get sidetracked from their primary mission. Interaction with NPC's along the way is hardly a necessity, and yet Benchleydale is a realm that's been sufficiently saturated with opportunities for sub-plots and side-missions.
To create the realm leading up to the module is one very important task for a DM. To maintain a working knowledge of the realm is another very important task of a DM. Knowing where the party might find the Hand Of Vecna or a Deck Of Many Things is just as important as knowing the primary mission of the party. Knowing that Okarr The Magnificent might dispatch the party on a quest, sending them four days' travel in the opposite direction from the hill giant fortress, is all just part of the grand design of the game.
As DM, one always ought to let the party have the freedom to do whatever they choose to do. Steering the party towards once particular destination all the time isn't really the way that the game is meant to be played. Let the campaign breathe. Have it be a colorful experience, and not simply a static (or cliche') experience. Be quick with a random encounter whenever appropriate, and allow the players to enjoy as much of the realm as they'd like to explore (before they dive headlong into the module).