During prototyping, you should stress reflective action over contemplation. Continuous active experimentation provides a great way to uncover new insights and directions and will greatly accelerate your learning process. Building low-fidelity prototypes with varying foci, which can be tested with key stakeholder groups also decreases the chance of investing in ideas that do not show sufficient market potential.
One of the core principles in many popular agile innovation approaches like lean startup and design thinking is iteration. Iteration means that the proposed models are not intended to be used in a strictly linear way, but instead allow entrepreneurs to move between different activities more dynamically. This becomes especially powerful if you take the interplay of divergent and convergent thinking into account. While divergent thinking provokes the generation of multiple choices, convergent thinking stimulates the narrowing down of choices to a few promising favourites. Both modes of thinking must be stressed at different times during a project. Be aware that different people (e.g. team members) and disciplines usually have a preference for one of the two modes.