The term "forcing" has always seemed a little harsh when referring to bringing flowerbulbs (tulips, hyacinths, etc.) into their flowering cycle prematurely in pots. "Enticing" or "tricking" seem more appropriate.
To force flowerbulbs, we want to fool them into reacting as if they have already undergone the cooling period that bulbs planted in the ground experience over winter. To do this we need to pot them up and place them in a cool location for a long enough time to undergo the enzyme change within the bulb that causes the bulb to start its growth and flowering cycle. It isn't hard to do.
Although any hardy bulb can be forced, some varieties are better suited to it than others. Very tall tulips, for instance, are not good candidates because they tend to get leggy and flop over when forced indoors. When shopping for bulbs to force, look for designations on the package that say "Good for forcing." This indicates that the bulb producer has found this variety to have qualities that make it a good candidate for forcing. After selecting your bulbs, get some pots (plastic is best) to use. Pots for forcing are generally about half as deep as they are tall. They are referred to as "bulb pans." For hyacinths, tulips, and daffodils a bulb pan about 6" deep is perfect. Crocus, iris, and other smaller bulbs won't need a pot more than 4" to 5" deep. Place 2" of soil in the bottom of the pot, then place the bulbs in the pot pointy side up. The bulbs should be placed very close together, almost touching. Then fill the pot the rest of the way with more soil and water thoroughly.
Now your potted bulbs are ready for their cooling period. They need to be chilled to a t least 40 degrees for at least three months. This can be done in an unheated basement, or in a spare refrigerator. It is also possible to chill them in the garden. To do this, dig a trench in your garden deep enough that the rim of the pot is at, or below, soil level. Line the bottom of the trench with straw or mulch so the pots won't freeze to the soil. This will make it easier to remove them when it comes time to bring them in when you want them to begin growing. Then fill in the trench around the pots with more sandy soil. Cover your trenched bulbpans with straw or salt marsh hay. Be sure that they stay moist. It's OK if they freeze. Bring them in about 4 to 6 weeks before your want them to flower.
Paperwhite narcissus are not a hardy bulb and can be forced without cooling them. For these, I like to use a glass bowl filled with stones so I get the added interest of watching the roots grow. Simply nestle the base of the paperwhite bulb into the gravel, again placing the bulbs so that they are almost touching. Fill the bowl with water to just BELOW the base of the bulb. Don't let the bulbs sit in the water since they might rot. Then, just step back and enjoy the show. Have fun!

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