We always cook our lakers in foil on the coals - super easy.  We filet and season them (butter buds, lemon pepper, onion, cajun, etc...) and cook them skin side down on the foil.  15-20 minutes tops.  We make little foil tents with a folded tab on the top to grab on to to remove from the coals.  When they're done, the skin will stick to the foil and you can pull the meat off easily.  This method is excellent, but its hard to mess up fresh lake trout.

If we have limited foil, we'll put 2 filets in the foil, skin on the outside, and the pack gets turned once while cooking.  It doesn't taste any different, just takes longer to cook.  

Never tried this with other fish, though.

Now I'm hungry.