PowerPivot Tips and Tricks - First Findings

I just finished a little project with PowerPivot together with James Beresford, and I feel compelled to share some of the lessons I learned during these exciting if a little bit stressful few days. There are a few things I have heard in the past in regards to good PowerPivot model design, but I'd like to re-iterate some, and maybe add some more to what other bloggers have already mentioned. As it is usual with my posts - the following is not an exhaustive list, but may resonate well with newbie PowerPivot developers like me (which at this stage is probably 99% of Total).