Amsterdam doesn't have a lot of tourist attractions like some other cities do. If you're there in the spring time, definitely spend some time in the Tulip gardens and rent bikes to go around the city.
If you're there during the winter, spend some time in the Van Gogh Mueseum and the other Mueseums surrounding. They are absolutely incredible and have great works of art.
No matter what season you are in, visit the Anne Frank House. It will be one of the best things that you do in your entire life. Other popular areas are the Red Light District and the Bulldog Amsterdam.
I would try to go here when it is a bit warmer. When we went, it was cold and snowing, and we still absolutely loved it! We can't even imagine what it would be like in warmer weather.
Make sure you stay right in the city center! Everything is so central that you don't want to miss the ability to see everything.
Amsterdam is known for it's stroop waffles. Google the best stroop waffle in Amsterdam, and go to that bakery. You will love every single one you try!
Amsterdam is also known for their french fries with an incredible amount of sauce on them. Try them and try the sauce! We had these fries about 10 times.