General information for most cut flowers and foliages to extend vase life.
Cut Flowers
Re-cut about 2 cm off the bottom of the stems at an angle. Remove excess foliage below the water line and use flower food or alternatively make sure the water is fresh every day.
Most cut flowers last even longer if you cut their stems shorter. So if you don't need them to be tall in the room you are putting them in, try cutting them down. This can extend the vase life of some flowers by up to a week.
Flowers in Floral Foam
Top up floral foam with clean water daily. Do not over-fill. Floral foam is like a sponge - unless you top it up with additional water it will dry out.
General
Do not place your flowers in direct heat, sunlight or draughts.
Do not put flowers on top of heaters, microwaves or any place where there is additional heat.
Some of the "household remedies" such as bleach, sugar, lemonade, etc. in the water can be quite damaging to particular types of flowers. As general rule, keeping the water fresh and using proper flower preservative are the best options.