Comment by namuol

1. Look at existing designs for inspiration.

2. Draft a prototype with a tool that's easy to hack with.

3. Try out your design with strangers; take notes where they get confused.

4. Change the design to address issues from #3.

5. GOTO #3

When drafting your design, don't worry about how it looks; focus on clarity and easy of use.

Note: There are many prototyping tools out there; this is a great resource: http://prototypingtools.co/