Evacuate the room that has the biggest mosquito infestation. Spray a water-based insecticide spray all over the room. Shut the door, and keep out people and pets for at least 24 hours. Not only can insecticide spray "catch" mosquitoes and kill them right away, it can also kill those that come into contact with a sprayed surface later.
Spray mosquitoes in your yard with an aerosol insecticide spray. These can also be harmful for people and animals to ingest or inhale, so make sure they're out of your yard before spraying. Shake the can and spray it directly on the mosquitoes to kill them fast.
Hang up flying insect strips. These are used to quickly catch insects such as flies and mosquitoes. Hang them in areas that are prone to mosquito infestations -- indoors and outdoors. Mosquitoes fly directly into the strips and get stuck in them.