When choosing eggplants, always opt for one that is shiny and
firm (not wrinkled or dented). My favourite way to cook eggplant
for baked dishes like moussaka:
Slice the eggplant into 1cm slabs.
Salt, and leave to "bleed" for a few minutes, both sides.
Wash well to remove salt. Pat dry with paper towel.
Blacken both sides under a hot grill.
(I feel that the blackening of the surface gives a sweeter flavour)
Then use to contruct your moussaka, bake, etc.
I use the same method to make Baba Ganoush.
Once grilled and cooled, place eggplant slices in food processor.
Add garlic, cumin, plain yoghurt, lemon juice and lots of pepper.
Blend until smooth-ish (still a little lumpy).
Delicious with paprika tortilla chips.
For a bit more flavour (or for BBQ eggplant steaks) try marinating
the slices before cooking. Anything you like - soy sauce and honey
or garlic is nice.