Primary: Climate and ripeness at harvest dictate the primary flavor profile of all Rieslings. Grapes picked at just ripe result in bright citrus driven wines. Those either picked later, when much riper, or from warmer climates where the ripening process is expedited by warm days and nights, will have juicier peach, melon and pineapple flavors and will feel much heavier in the mouth. High acidity will remain in either style as will undertones of blossoms and flowers.
Secondary: Riesling is almost never exposed to oak, lees or malolactic fermentation, all of which create subtle to bold secondary flavors in white wines.
Tertiary: Petrol, petrol, petrol! Not the kind of overwhelming gasoline smell from your local gas station, but still very distinct and unmistakable. Younger vintages will have more faint petrol smell, but those which have been aging for longer periods can have much more distinct petrol which sticks around a while. The good news is Rieslings do not taste like gasoline!