Prototyping is an important part in our design process as it saves time in a long run. We would rather throw away drawings of wireframe prototypes than to throw away weeks worth of development code.
We have a few prototyping methods we use depending on how much time we have for a certain project. The quickest way is through paper design sketches, where we sketch out wireframe designs and run through them.
The more complete method is through the use of one of our favourite online prototyping tools, Invision. Invision allows us to experience our wireframes first hand on our mobile device itself. This gives us a real feel of how things would play out in an actual use case, allowing us to better identify weak links in our designs.