Keep in mind that it's better to cut flowers the day before you plan to arrange them. Place them in a deep bucket filled with lukewarm water, and allow them to sit in a cool location overnight. When you cut flowers from your garden, you're doing your plants and yourself a favor. If you remove flowers before the plant can set seed, you strengthen the plant by sparing it the energy that would've gone into seed production. And many plants will rebloom if cut back after the first flush.
Tulips tend to droop once they've been cut.
To correct that tendency, roll cut flowers tightly in newspaper, and place them in a bucket of warm water overnight. This will toughen up the stems and encourage them to stay in an upright position. Seal the cut ends with the flame from a match or lighter to preserve them longer. Or plunge the cut stems into boiling water for 30 seconds. Remove roses' foliage and thorns before arranging them.