You will know it is time to divide your daffodils when the plant produces a lot of foliage and small flowers. This is nature's sign that the daffodil needs to be divided because the soil does not have enough nutrients to feed the bulb mass. When this occurs the plant will start sacrificing flowers to survive. By dividing daffodil bulbs, you will perk up the plant and reap larger, healthier blooms.
Use a garden spade, and dig up the daffodil after the foliage has died. Try not to damage the bulb as you dig and lift it from the ground.
Look to see if the bulb is a single bulb or a bulb mass. If it is a single bulb, replant it. If it is a bulb mass, shake off the excess dirt.
Hold the bulb mass in one hand. Use your other hand, and grasp onto a single bulb. Gently shake it until it becomes loose and frees itself from the original bulb. Repeat the process with each bulb. If the bulbs are stubborn and will not free themselves from the original bulb by being shaken, run the entire bulb mass under running water and shake them free.
Plant the freed bulbs and the original bulb back into the ground. Place the bulbs in the ground at a spacing that is ascetically pleasing to you at a depth of 5 to 6 inches.
Cover the holes with soil. Water immediately.