Prep your flowers by measuring how long you want them to be and trimming them all about equally, trimming at an angle. You want them about 4-5" longer than the vase when positioned diagonally.
Remove any leaves that will fall below the base of the vase.
Fill your vase with water. Add flowers diagonally across the vase, criss-crossing stems and allowing them to fall to each side of the vase.
Start filling in {alternating a few blooms of another color or style if you choose} using the existing stems to help you position new blooms, leaving some vertical.
Trim eucalyptus (or other greenery/filler) to be an additional 6+" longer than the flowers themselves, and again remove any leaves that would fall below the base of the vase.
Insert eucalyptus (or other greens/filler) around the edge of the vase all the way around or at 3 opposite points.
Add small stems of filler or greens, nestled in between the blooms at opposite points in the flower arrangement and adjust stems as needed to appear full.
Notes
Many blooms open with time and become fuller - this centerpiece becomes more beautiful as the days pass, just refresh the water.If you don't like how it looks, adjust. Small tweaks can make a big difference in the overall look of your arrangement! The smaller the vase opening, the fuller your arrangement will look.