Summarize the following:
There is some debate regarding how helpful floral preservatives are when arranging cut tulips. While some argue that tulips do not need powdered plant food, there is no evidence to suggest that this preservative will hurt the flowers, so you can add it as a precaution if desired.  Floral preservative can be purchased at nearly any floral shop. Some may even come with your tulips when you buy them. Sprinkle the preservative in the water and let it dissolve before arranging your tulips. Add more preservative each time you change the water. This includes direct sunlight, radiators, stoves, lamps, and television sets. Heat can cause the tulips to run through their lifespan at a more rapid pace. As a result, your arrangement will not last as long as it otherwise could. Tulips are heavy drinkers, so you should check the water level twice a day and add fresh water at least once a day. To improve the health of your tulips, it is wise to completely change the water every three or four days. Changing the water as soon as it starts to look cloudy minimizes the amount of bacteria in the water, thereby increasing the overall lifespan of your flowers. Each time you change the water, you should also trim the bottom 1/4 inch (6 mm) of the stem using a sharp, clean knife.  Regularly trimming more off the bottom of the stem removes decayed stem that could otherwise block the rest of the healthy, active water uptake channels. As a result, the stems can draw water up more easily and for a longer period of time. Keep the stems submerged under water while cutting them.

Summary:
Consider adding plant food. Place the tulips away from sources of significant heat. Refill the water. Trim every few days.