V1: Neat. Scotch in a glass all by it's lonesome.
V2: On the rocks. Scotch with little squares of really hard water.
V3: Scotch and Water. As it says, scotch with a splash of water, preferably scottish mineral water.
V4: Mixed. This is a sin, anyone caught doing this shall be forbidden from ever drinking scotch again, and will also be reported to the proper authorities.
There may be more, these are just the methods I know.
With a single malt I take it neat, so I can get all the tasty little nuances, but with a blend I'll go with on the rocks, and blends taste better cold anyway.