These are some of the basics you will need to know in order to properly view the redesign of anything. Peruse the pages and blog posts to get ideas on designing a huge variety of items.
We have a comprehensive page on general design but if you are interested in looking into it in more depth, try these sites:
These sites are two of our favorites and will point you to a ton of design basic information. Once you begin to grasp the concepts, you will naturally start developing a critical eye toward looking at everything with a focus on how to make it better.