When coming to the Netherlands, be flexible: pack an umbrella (or two—the topography results in a blustery wind, which makes short work of a lightweight frame); bring a raincoat, with a thick liner in winter; and always have a sweater or jacket handy. For daytime wear and casual evenings, turtlenecks and thicker shirts are ideal for winter, under a sweater. Unpredictable summer weather means that a long-sleeved cotton shirt and jacket could be perfect one day, whereas the next, a T-shirt or vest top is as much as you can wear, making it hard to pack lightly. Bring a little something for all eventualities and you shouldn't get stuck.
Essentially, laid-back is the norm. Stylewise, anything goes. Men aren't required to wear ties or jackets, except in some smarter hotels and exclusive restaurants; jeans are very popular and worn to the office. Cobblestone streets make walking in high heels perilous—you don't want a wrenched ankle—and white sneakers are a dead giveaway that you are an American tourist; a better choice is a pair of dark-color, comfortable walking shoes.
Women wear skirts more frequently than do women in the United States, especially those over 35. Men need only include a jacket and tie if you're planning to visit one of the upper-echelon restaurants.