i usually take it neat. it just doesn't feel like something to dilute.

not to sound like i'm stuck up my own ass, but cognac needs to be savoured. i've never encountered another beverage that can change so much just spending time in a glass. i can spend the first 15 minutes just sniffing, not drinking any, and the taste sorta... develops. the tip i got years ago was smell-swirl-smell. the traditional cognac glass exists to keep the volatiles from escaping, and swirling releases more of them, which makes the aroma different. as you go up the grades the aroma becomes more complex. it's really interesting.