I have to admit I still find the whole flight-plan thing very easy from a practical point of view, but near-impossible from a legal point of view.
I was very confused when I re-read some of my air-law notes and discovered I needed to file a flight plan to fly VFR in Class D. I've flown VFR in Class D many times, and never completed a flight plan! Then I discovered that, by calling up ATC on the R/T and passing them your flight details, you're deemed to have filed a flight plan. But the same procedure isn't sufficient for filing a flight-plan for an international flight.
My advice to you would be as follows: for your Air Law exam, just learn what the text book says, regurgitate it if asked, then forget it. Then you can go and learn what you actually have to do in practice. I wouldn't recommend this technique normally, but I think it's good advice for filing flight plans.
FFF
------------