Well, earth is naturally sturdy and rigid. As it is one of the most sturdy elements out there, it is usually used as a great form of defense in most cases. Earth is also powerful and versatile, being able to do both concussive, or piercing damage depending on the infused characteristics given to it (where a large pillar can cause massive internal damage, and an earth spike can cause great piercing damage.)
As for earth and other elements,
Earth is naturally weak to lightning, as lightning release has the ability to enter the earth and break it down to its basic components, making it crumble and degrade which is never good for it. However, when combined with lightning, earth could also be used to increase the range, or characteristics of a lightning attack. Lightning when used to attack through earth can add a form of dust or mineral damage that can reduce the field of vision somewhat, or cause annoyance on the opponent's part.
Earth and water have a unique relationship. While earth is strong against water for being able to completely block or even absorb the water, earth and water combined have an advantage in battle. Earth can be used to create a finite space in which a water attack can move, as well as creating walls in which water may be directed in certain ways. Water and earth can also create mud, (although in the manga and anime it is shown that mud is also considered simply earth release without being combined with water.)
Earth and fire are both powerful elements but are nearly opposite in nature. Earth causes mostly internal bludgeoning damage, while fire almost always caused outward surface damage. While earth can block fire about as well as it can block other elements, when used with or against fire, the fire can heat the earth release to great temperatures, either fracturing it, or melting it depending on the level and heat of the fire. Theoretically, when using earth and fire in conjunction, the earth could be heated using a large scale fire release technique which could add bonus burning and searing damage to the earth, while also partially giving the earth fluidity. Incidentally, Earth is a major component in the KKG, Lava release. As lava is 50% fire and 50% earth, earth is a huge factor in its creation, whereas earth is the base, and fire gives it the heat and movement necessary to create lava.
Earth and wind are near polar opposites. While earth does internal damage through bludgeoning, wind is greatly used for its cutting properties. And while earth is mainly used for defense and less often for offense, wind is mostly used for offense, and less so for defense. Lastly earth is almost always performed by using existing earth, while wind almost always is created by the user. Earth could possibly be used to create a smaller area in which the wind technique could be used, which would increase the power, as the wind would be more focused on one area.
Earth is also a component of the Kekei Tota, Dust release, along side wind and fire. When looking at the elements combined to create this technique, i would guess that the Wind element is used to create great speed, while Fire Release in incorporated in the heating of anyone or anything caught in its range, and the Earth aspect creates large amounts of "debris" which are thrown about by the wind and heated with the fire, allowing dust release to essentially bludgeon the target into microscopic dust, effectively destroying it.