Few things can ruin a back yard get together like mosquitoes. Commercial products exist like bug zappers and citronella candles but here are a few home-based devices and tips that you can use to help reduce mosquitoes.
Bubble Machines - Load up a bubble machine and let it run before and during your outside activities. The soap makes it impossible for mosquitoes to fly. A few drops of lemongrass oil added to your bubble solution will also spread a deterrent as well. Home made bubble solutions are cheaper by the way.
Incense - Cheap incense sticks soaked in citronella oil and dried can replace mosquito coils at a fraction of the cost. Stick them in the ground and in nearby flower pots or arrangements and light them.
Listerine - Use a hand held pump bottle filled with 4 ounces of water and 1 teaspoon of Listerine to spray your deck, lawn, bushes, etc., just before guests arrive to help keep mosquitoes away from the sprayed areas for a few hours. One half teaspoon of dish soap added will help to kill any larva also.