Comment by kylejlarson

I usually start with pen/paper because I find it the fastest to get a bunch of ideas out. Then from there I'd go with whatever tool you think will be most efficient. I personally use Balsamiq because it's really quick & easy (drag/drop) and then if my first wireframes need drastic changes it's still quick to change. I'm then taking these wireframes to clients or teammates to review and improve before focusing on design. If you're going to end up using a design tool for a high-fidelity version you can use Sketch or Illustrator for wireframes, the only downside is getting too focused on pixel perfection at an early stage. I like keeping the process pretty flexible, sometimes you can pass a wireframe to a front-end dev if you've got a solid style guide, other times you want a high-fidelity design or a prototype.