I build my adventures as flow charts.
If I want tons of loose ends, I start at the line with a single entry (such as, the party is hired by X to do Y). They go through the flow chart, and every decision, person, or location they pass up becomes a potential future plot hook.
If I want the party to accomplish a specific goal, I build it the other way around - a lot of hooks which lead to fewer and fewer alternative decisions as the adventure goes on, leading to a single climactic conclusion.
Note that I only make very general notes on each "node" in the flow chart, as my DM style is to improvise and react.
With both alternatives, above, you can accomplish specific things while ensuring the players feel they are the ones driving the adventure. The way I improvise many of the details allows me to deal with the party doing unexpected things and still keep the adventure intact.
Hope that helps.