Eliminate the conditions in which bugs breed by draining any containers with standing water, such as flowerpot saucers, roof gutters, and birdbaths.
Encircle your patio or deck with citronella candles or incense sticks so the smoke and fragrance that the bugs hate will always waft toward you.
An alternative: Plug in some fans. Mosquitoes are weak flyers, so even a fan set on low will create enough airflow to keep them away. This works best in a small area, like a deck, where you can set up two or three box fans around your guests. It’s also a good idea to put a tabletop fan near the food.
Apply a bug repellent. For those containing DEET, choose 10 percent to 35 percent. (The American Academy of Pediatrics recommends that DEET be applied to children no more than once a day, and does not recommending using it at all on infants under the age of 2 months.) If you prefer to go DEET-free, natural bug repellents can be quite effective (one to try is Coleman Botanicals Insect Repellent, $7.50; rei.com).
Stay calm. Swatting at mosquitoes attracts them, since they're drawn to motion.