How to prepare courgettes/zucchini?
When they're still young, I grill them -- 


trim ends
cut into planks about 1/4" to 3/8" thick (~1cm)
toss in olive oil
sprinkle with salt
grill over direct heat
flip when you develop good char marks.
pull from the grill once the other side is slightly charred.


As they get older, the seed cavity starts developing -- you can cut the sides off, leaving the middle, but it's just not as sweet.