It’s tempting to map out and develop a large model with lots of features, all on an equal basis. That approach is best suited to exploring shapes and relationships on a throw-away, prototyping basis. However the result is unlikely to be manageable to the end of the design phase. It does not anticipate the visualisation stage and will probably be hard to maintain, enhance or update.
Instead it’s usually best to work out what’s important to model in detail and keep the rest sketchy. A handy tutorial by a practitioner* Jim Leggitt gives crisp guidance on a structured approach to making a complex model manageable here.
*He is an architect, urban planner, professional illustrator, educator, writer and more besides. interview.
His pioneering speciality combines hand drawing with digital 3D modelling: like this.