The first mistake that most make is by having excessive moisture problems in their yard especially near the foundation of the house. If you notice standing water problems in the yard after it rains, get these dealt with. Leveling out the soil or installing a drainage system will take care of this problem. Also install rain gutters along the roof so that you can keep moisture from getting into the soil near the foundation of your home. Consider draining this moisture into a rain barrel as it will help keep as much of the soil dry as possible
The second big mistake that is made is having wood that is against the house. Most of the time people will stack wood against the side of the house to give them easy access when grabbing some firewood during the colder months of the year. This will invite termites, as the woodpile is a great source of food. As the colony grows, it will get into your house as well. Another source of wood is the bushes that are next to the home. Keep these pruned and make sure they do not grow into the side of the house as this gives termites and even carpenter ants easy access to your siding. If you do have a flowerbed next to the house, be sure to not add wood chips and mulch at all.
The third mistake that is made is having wood structures in the yard that touch the soil. Make sure to always have a barrier between any wood structures and soil. This is best done with concrete although it can also be done with sand as well as it will stay relatively free from moisture. If using wood for structures like a shed or deck, try using chemically treated wood that helps prevent termites at least for the wood that is closest to the ground.
While avoiding these mistakes will help prevent quite a few problems, it is still a good idea to have regular termite inspections from a trusted company. A regular inspection will find any problems at the earliest stages helping you save more money as massive damage will not be caused.
Be sure to go out today, identify the problems, and clean up the yard so that you will not be making these same mistakes to prevent as much termite problems as possible.