Get rid of any food that you are in the habit of leaving outside, or pet food that the birds can smell. Either can attract pigeons.
Install netting over popular pigeon nesting sites. Nylon wire will not be effective, but chicken netting or a more solid kind of screen, nailed over the area where pigeons would otherwise nest, is very effective.
Attach permanent spikes, made of wire or glass, to areas on your home or in your garden where the pigeons congregate. This makes for a hostile environment, and the pigeons will learn that your yard is not the most enjoyable place to be.
Scare the pigeons off by pelting them with water, or placing a large replica of a pigeon predator in your yard. Through repeated doses of water, the pigeons may learn that your yard is not an enjoyable hangout. The predator, assuming that your pigeons aren't smart enough to figure out that it isn't real, may well be effective.