First, the traditional whiskey to use in a Manhattan is good old American rye. It should be Old Overholt, made in Kentucky. For a change of pace sometimes use a straight bourbon like Maker's Mark.
The bitters can be Angostura, Peychaud's Aromatic Cocktail bitters, or Regan's Orange bitters. The orange bitters mix nicely with the flavor added by the maraschino cherry so that's what we recommend.
Finally the question of vermouth. Many recipes call for 1 part vermouth to 2 parts whiskey. We find that much can detract from the flavor of the whiskey. The "Perfect Manhattan" recipe calls for equal parts sweet and dry vermouth which creates a nice balance. Our recommendation is a splash of each (slightly less than a capful).
1. Pour 2.5 ounces of rye over 5-6 ice cubes in a martini shaker
2. Add a scant capful each of sweet vermouth and dry vermouth, and 2 dashes bitters
3. Shake and strain into a chilled martini glass over 1 marschino cherry
4. Sip and repeat until giddy and wobbly
Note: If you're not wearing a collared shirt you're underdressed for Manhattans (or cocktail hour for that matter).