Compared to many other plants echinacea are very easy to propagate. This combined with the new varieties of colors and lack of care necessary, have propelled coneflower to the top of plant lover's list. The most effective way of increasing your number of coneflower is through division.
There are two keys to getting healthy divisions of echinacea. One, make sure you take good sized divisions of the plant and be sure to include the root systems. Two, after planting, keep it moist but not wet. Let the plants dry out before watering. More coneflowers are lost from overwatering than have ever been lost to dry conditions.
When dividing, don't be greedy. Three live plants is better than 10 dead ones. Many people tend to divide the clumps into to small pieces trying to get as many plants as they can. A good coneflower division should be 2 and half to 3 inch squares. Dividing should be done with a sharp knife (be careful, you'd hate to end up with 6 divisions but only 4 fingers). I like to trim the top off in order to let the plant concentrate on root growth rather than top growth because the top growth is probably going to die back anyway.
I prefer to take these divisions and start them in small pots but it is perfectly acceptable to put them straight into the ground. Just make sure the soil is worked up to allow quick root growth.
Timing is not as important as other plants when it comes to division. As long as the plant is pushing new growth, echinacea can easily be divided. It can also be divided when dormant but keeping an eye on water during these times are essential to preventing rot. I recommend March to Sept.
Seeds are a different approach. Division gives you an exact clone of the plant, where seeds give you a random selection of mother nature's work. You never know what you are going to get because most of the seedling don't stay true(show the characteristics of the mother plant). A tried and true, although odd looking, way to collect seed is to allow the flowers to fade, then cover the flower with a piece of panty hose or paper lunch bag. This allows air flow and the seeds to dry, but won't allow the seeds to blow away in case you don't get out there at the right time.
Once you have the seeds, they require 60-90 days of cold (31-38˚) stratification. This can be achieved by either sowing the seeds in the fall or my preference, putting them in a plastic bag or pill container, put them in the refrigerator and plant them in the spring. I like to start them in flats in the spring but many people are very anxious to see the new plants and start them inside. Inside is OK as long as they get enough light and aren't over watered. Seeds germinate very quickly, 10 days, but should be left in the flat for them to "harden off".
Whether you chose division or seed, just the fun of creating new coneflowers will be something to enjoy. If you go the seedling route, who knows, maybe you'll create the next great coneflower.