If you do add water, how much?

[MacKenzie]

No preference one way or the other. I'll always try a new scotch neat first. If I like it that way I'll usually leave it alone... for a while. But with each one I usually try it with a bit of water and/or an ice cube or two. Experimentation. Some scotch "opens up" with a bit of water or ice and some simply gets diluted.

And, as Jock said, it also depends on the mood.