Remedy for flies/bugs from getting in house?

Flies are just bad around here. It is more than annoying when you open the kitchen door and the flies or bugs will follow right on you. So i thought killing them using the sprays won't do good because theres a lot of them outside that are just ready to sneak in anytime you open the doors. Always spray is also not a good idea since we have kids in the house. Anyway today, i went online and search for remedy on how to, just at least keep the flies away from getting in the house and I saw lots and lots of suggestions from different websites. The most common suggestion was to hang a ziplock bag with a quart of water in the doorway. I thought its kinda silly but people says it work. And actualy some of the restaurants or vendors are using the trick also. There is no specific reason how it work but some says the bag of water will scare the flies away because of the reflection of the water. Kind of silly but it won't hurt me if i try, so yeah i did. Husband just laughed at it. Another thing is to hang a cd in the doorway also because the flies and the bugs thought the reflection of the cd are the eye of their predators, so its another thing that would scare them away.