As I build up others I’ll add them to this entry.
One of the more useful (or annoying) items you can collect on the track in Mario Kart 7 is the “spiny shell” (or the “blue shell” as some people might call it). It’s great when you are further back in the pack but a right, royal pain if you are in first position and you keep getting pelted by blue shells.
I figure, if it’s coming for you then you may as well take out your competitors in the process. Slow down or stop to allow your rivals to catch up just as the blue shell is going to hit and you’ll all be hit. At the very least, you and your rivals will be level instead of them zooming past you while you recover from the attack.
Similarly, if you are in second position be wary of whoever is in first place suspiciously slowing down as they may be trying to use the above trick to stop you from taking the lead too easily!