Do you have a process you follow when starting a new project?
I have written something on this topic lately: http://www.svenread.com/product-development-process-flaws/. Perhaps it is of interest for you.
Great article and a big help.
This might be useful as well: https://sites.google.com/a/khanacademy.org/forge/for-developers/design-iteration-at-khan
I use the Design Council's Double Diamond method: http://www.designcouncil.org.uk/about-design/how-designers-work/the-design-process/