Make sure anything that holds water is emptied. That's where they lay their eggs. If you have a fountain, put some olive oil in it. It forms a coat on top and won't allow the mosquitoes to lay. Keep leaves raked and removed as they will hold moisture as well as a hiding place for the pests. I had someone recommend an all natural spray they found at Lowe's. I haven't used it, but they said it worked great. I can't remember the name, but if you read the labels, you should find it.