Heh... *remembers his Music Theory class a few years ago*

Try having a teacher tell you to demonstrate the effect each mode has on a fixed melody. (I picked 'Mary Had A Little Lamb.' It sounds downright scary in Locrian)

As a sidenote, if you can think about chords by using numbers (it's how I learned, but I'm told that many people don't do this), there's another way to remember which modes are major/minor sounding.

Start with Ionian mode (standard, vanilla major scale). I'll use C in my example. The chords go like this:

I - C Major (tonic)
ii - D Minor
iii - E Minor
IV - F Major
V - G Major
vi - A Minor (relative minor)
vii° - B Diminished

Then compare that to a list of the modes, in order.

Ionian - Major-sounding (natural major scale)
Dorian - Minor-sounding
Phrygian - Minor-sounding
Lydian - Major-sounding
Mixolydian - Major-sounding
Aeolian - Minor-sounding (natural minor scale)
Locrian - Diminished-sounding

See the similarities? (Has helped me a lot when someone pulls a piece I've never heard and says "It's in key of x, Mixolydian mode!" Thought process: "Okay, that mode is the ... fifth one down... that's the ... dominant chord... piece will be ... predominantly major... I think...?") Works most of the time.

As part of our research, we got to analyze an old church piece written in each of these modes, except Locrian (we used a modern piece for that one). Turns out, the Church banned the use of Locrian mode as a tool of the devil, because harmonizing within it has so many tri-tones (tones as far apart as C and F# on the keyboard played in harmony; same tone used in train whistles and - though arpeggiated - in the 'Simpsons' theme music) and dissonance.

All that being said, modes still throw me off when I'm learning a song. For some reason, when I see "Fb" as a note on a sheet of musuc, I get confused. Trying to anticipate chords in a modal (not Aeolian or Ionian) piece is also difficult when you're used to playing in one of those two. I've been through 3 years of Music Theory and who knows how long of playing modal pieces, and I still learn something new with every thread created about these nasty buggers created just to make folk singers'/musicians' (not that singers aren't musicians, just that 'players' didn't sound right) jobs harder.

Hope some of that helped! If I've confused anyone, or if you want me to pull out my textbooks for a better/more detailed explanation, feel free to PM me!
-J