Step One as always will be to make a drawing on paper, preferably with pencil, though I used a Pen here. The layout, elements, white spaces are all mentioned in a rough manner. It is important that the design does not look busy or over crowded. We would not be thinking about colors or font faces at this point. And I made this mockup for the promo.
Next step is to fire up a graphics program, in my case I am comfortable with Adobe Fireworks. It is quite easy to learn and work with especially for doing designs like this and also for web developments.
You can digitize the drawing if you want and keep it in a background layer of the application as a reference or visually look at your drawing for reference.
Once you start with the digital tool, it's important that you choose and use few fonts and colors. The colors used for the promo poster here are taken from the application itself, a shade of blue. Limit the use of fonts, usually one for headings and another one for body. And that's pretty much that for this design :)
