The Boston Wine Expo is HUGE and needs a plan to attack. You can't just drink everything there! Take a notebook, and map out the wines you want to taste. Start with sparkling, then try whites, then reds, and finally any ports, sweet or fortified wines. That gives your taste buds the best possible chance to appreciate each set of flavors. Also drink a lot of water!
Of course when we did this expo tasting, we went for the dessert wines first :)