Begin with an immaculately clean pail or bucket. Some good hot water and anti bacterial soap is an ideal beginning. Scrub your pail well and rinse with very hot water. Dry completely before beginning to avoid contaminating your cut flowers.
Make sure your knife is sharp and clean it also with the anti bacterial soap.
Using good warm water, about 100 degrees, put a few inches of water in the pail right before you go out to cut flowers and greenery.
There are commercial products you can add to your warm water. You can choose a good commercial plant food or flower food. If this is not available, make your own. One type is made of 1-teaspoon chlorine bleach and a tablespoon of sugar to a gallon of water.
Flower stems have to have a hollow interior for water and nutrients to move up from the soil to the flower or bud. When you cut a flower, the most harmful act is to cut the stem straight across. You should cut at an angle. A flat stem going into a flat pail means very little water can go up the stem.
This hollow interior can be closed off at the time of cutting. This is called an air lock. Flowers and greenery can wilt quickly if this air lock occurs. So an angle cut helps make it possible for water to move. When the flower is cut the part of the stem that includes the water ducts has some vacuum. If this is closed off, water does not feed the flower.
When you cut the stem, immediately put it into the pail as soon as you cut off the bottom leaves. These need to be cut so no leaves are below the water. Those below the water can become rotten and make the water smell bad. Nothing but the stem itself goes into the water.
A jagged cut of the bottom can cause damage to the stem tissue. This can produce bacteria just as bad as if the leaves were put in the water. So the knife should be sharp as well as clean.
It is a good idea to leave the stem and flower in the conditioning solution at least 3 hours, but some choose to do so all night.

The best time to cut flowers is early morning when the stem has the most moisture in it. Also watering early evening then cutting later when the water has soaked into the soil will work.

When you buy flowers from a store, it is wise to remove any sleeve or elastic band and place the stem into the conditioning stem water.

If the stem ends are clogged, the water will not move up the stem from the vase or other container you put your flower arrangement into.

When you are making your flower arrangement, you can use a good commercial flower foot in your water. If you have several flowers to arrange, using rose food may not be the best choice. A home made plant food can be made using 1 cup of regular 7-up plus ½ teaspoon household bleach and 1 cup of water. Cool water is better unless you have buds that you want to open. Warm water helps them open faster. These tips will help you condition your cut flowers.