Like AM DXing, FM DXing is a fun hobby that does not require a large initial investment. A basic FM radio is all you need to get started.
Tropospheric ducting is a common way that long-distance FM radio signals travel. This ducting occurs when a particular combination of temperature and humidity create a layer, or barrier, of ionized particles in the troposphere. When this layer combines with the ionosphere layer, a tropospheric duct forms. FM signals can travel along a tropospheric duct for hundreds of miles until the signals escape the duct and return to the earth's surface.
Sporadic E-skip is another fairly common method of long-distance FM signal propagation. It occurs when an FM signal bounces off a highly ionized patch of the atmosphere's E layer and returns to earth some 500-1,500 miles from the transmitter. The summer months are best for E-skip propagation.
Antenna height is paramount for optimum FM DXing. If you use an external directional antenna such as a Yagi design, you can aim the antenna to pull in specific, distant broadcast stations.