I only knew the vanishing point thing because of being an art student; You get taught about it when you're learning to draw buildings. It's the term they use to describe the way that all lines around you seem to head towards a single point, due to your perspective, if that makes sense.
Other than that, I didn't find it desperately hard and the bit of study I did really helped. I really enjoyed doing the estimate the seal population thing for some reason...
Trig will be my downfall; I didn't like the shadow thing.