Here’s a few tips to help keep your fresh flowers beautiful as long as possible:

When you first receive the flowers, check the water level of vased arrangements to be sure all the stems are in the water; add water as needed so all stems are well immersed
For wrapped flowers, as soon as you can, cut the flower stems at an angle with gardening clippers or a knife, and immediately place into room temperature (or lukewarm) water. Note that scissors will crush and close the stems vs. opening them.
Display the flowers out of direct sunlight, and in a cool location
Do not place the flowers near ripening fruit; the fruit gives off ethylene gasses which age the flowers
Change the water every 2 to 3 days. You’ll want to clean the vase so there’s no debris left in or on the vase. Trim/cut the stems, 1/4 inch. And, then replace with fresh water.
If a particular bloom is wilting, re-cut it as soon as possible, and replace in the water. Lukewarm water is best.
As the days progress, pull out any withered blooms and enjoy the longer lasting flowers.