Palate

How does it taste: is it sweet or acidic, fruity, floral, vegetal or spicy? Is it tannic? How does it feel on your palate: is it full-bodied, and does it linger in your mouth?

Run through your mental check-list of grape flavours and see which apply. Feel the structure of the wine as well - that will give you just as many clues. For example, if it’s white and smells and tastes of ripe apricots but has low acidity, it is more likely to be Chardonnay than Riesling, since Riesling is acidic.