Eliminate breeding grounds -- basically, anywhere stagnant water can accumulate. Don't allow cans, buckets, or wading pools to collect water when it rains. If they have, empty them immediately. Repair leaky air conditioners. Birdbaths, fountains, troughs, and dog dishes should be emptied and refilled daily; saucers beneath potted plants should also be emptied or filled with sand. If you have a pond, stock it with mosquito fish -- a minnow that preys on mosquitoes. (Don't worry about your swimming pool; the chlorine will keep mosquitoes away.)
Citronella, an extract from citronella grass, is often sold as a mosquito repellent, but its effectiveness is debatable. Commonly sold as a component of mosquito-repellent candles, citronella oil is also available and can be burned in tiki torches and other outdoor lanterns.
Wood smoke is another mosquito repellent. Since building a bonfire isn't practical, mimic the effect on a smaller scale by using mosquito coils, also known as smoke coils or cedar coils.
According to Consumer Reports, repellents cotaining DEET (diethyl toluamide) work better than any of the natural products on the market. May people object to DEET because, in high concentrations, it can cause serious side effects, such as dizziness, blisters, rashes, and confusion. As such, DEET should never be used in concentrations higher than 30 percent (most commercial mixtures are lower). Children should not use repellents with more than 10 percent.
If the infestation is serious, contact your local health department to find a mosquito-control professional in your area.