-Cut the stems at a 45 degree angle to improve the stem’s ability to uptake water. To help this even more, make some vertical splits on the bottom 1” of the stem; smashing that part with a hammer will do the same thing.
-Put the stems in a vase of water right away, trimming off any buds that would be below water level; they make the water spoil faster.
-Keep it out of direct sunlight, and change the water every 2-3 days so it doesn’t grow bacteria. You could also use flower preservative (still changing the water at least once a week); a homemade version is below.
The flowers should bloom in about three weeks, depending on how close to blooming they were when cut. If you cut them about a week before normal bloom time, they’ll only take 2-3 days to bloom inside.