Here's the information that I found at the American Mosquito Control Association:
Larval Control
Homeowners can take the following steps to prevent mosquito breeding on their own property:

  1. Destroy or dispose of tin cans, old tires, buckets, unused plastic swimming pools or other containers that collect and hold water. Do not allow water to accumulate in the saucers of flowerpots, cemetery urns or in pet dishes for more than 2 days.
  2. Clean debris from rain gutters and remove any standing water under or around structures, or on flat roofs. Check around faucets and air conditioner units and repair leaks or eliminate puddles that remain for several days.
  3. Change the water in birdbaths and wading pools at least once a week and stock ornamental pools with top feeding predacious minnows. Known as mosquito fish, these minnows are about 1 - 1-1/2 inches in length and can be purchased or native fish can be seined from streams and creeks locally. Ornamental pools may be treated with biorational larvicides ( Bacillus thuringiensis subsp. israelensis (Bti) or S-methoprene (IGR) containing products) under certain circumstances. Commercial products "Mosquito Dunks" and "Mosquito Bits" containing Bti can be purchased at many hardware/garden stores for homeowner use. Zodiac, a division of Wellmark International, has developed Pre-Strike Preventative Mosquito Control (PMC) product that kills developing mosquitoes using insect growth regulator (IGR) technology. Like Mosquito Dunks, Zodiac's Pre-Strike can be found at many home/garden and pet specialty stores.
  4. Fill or drain puddles, ditches and swampy areas, and either remove, drain or fill tree holes and stumps with mortar. These areas may be treated with Bti or methoprene products also.
  5. Eliminate seepage from cisterns, cesspools, and septic tanks.
  6. Eliminate standing water around animal watering troughs. Flush livestock water troughs twice a week.
  7. Check for trapped water in plastic or canvas tarps used to cover boats, pools, etc. Arrange the tarp to drain the water.
  8. Check around construction sites or do-it-yourself improvements to ensure that proper backfilling and grading prevent drainage problems.
  9. Irrigate lawns and gardens carefully to prevent water from standing for several days.
  10. If ditches do not flow and contain stagnant water for one week or longer, they can produce large numbers of mosquitoes. Report such conditions to a Mosquito Control or Public Health Office. Do not attempt to clear these ditches because they may be protected by wetland regulations.