Cut stems on a slant of 45 degrees - This will prevent the formation of an airlock in the stem.
Add flower food provided along with the flowers / tsp of sugar/ glycerine to a pint of water. A tsp of bleach reduces bacterial growth while 2 tbsps of lemom juice helps pH levels.
Remove all the leaves that will be submerged under water - These leaves will rot & create bacteria.
Change water & re-cut the tips of the stem every other day, if possible.
Take a clean vase & fill it with about 3 inches of water.
Ensure good ventilation, cool location & keep them away from hot/cold drafts.