I'm on a project that has complex requriements (no visuals), and I am the User Interface lead. I'm not sure where to start, I was thinking about conducting a white-boarding session to start brainstorming ideas. Any Suggestions?
Jon's answer is great and has the basics, but here's more detail in case you need it.
1) Figure out your audience. This could be customers, staff members, etc. Depending on your application you may have several types of audiences, and that's okay.
2) Come up with some user stories. These consist of roles and desires, involve both your audiences and requirements. Some examples:
Start broad with these and get more specific. This helps you figure out your workflows. More on user stories
3) Data Requirements. Figure out what you will need to get from your audience (roles) in order to carry out the tasks (desires). Focus on need here so your interface doesn't get bloated.
4) Start building workflows & wireframes. Start sketching out how the application will help your users (roles) get things done (desires). Make the workflows and interfaces as painless & simple to use as possible. Show the wireframes to other people (end-users if possible) early and often to see if you're on the right track.
5) Get it up and start testing. Once your workflows and wireframes seem to be adequate, build the thing and start going through your user stories to see if everything works. Then give it to some people in your target audience(s) and observe.
Don't be afraid of change. Along the way you will discover that some things don't work. You will probably need to rethink workflows and interfaces several times, but that's fine. The more work you do here will pay off in user satisfaction.
Talk to some users. We're currently doing some simple group interviews and surveys. The primary purpose of this is to learn what real people care about, so we know where we should focus our efforts. But also, by holding them in different employees' homes, we've got more than just the UX team talking about users. The company president, lead developer, and project manager now have faces to put to "the user" - not just the UX team.