Swat the flies with whatever you have when you see them. Honestly, I think you should keep the place clean, use fly curtains if necessary, and probably use some natural oils or herbs (e.g. mint, castor oil, lavender, etc.) to chase the flies away.
It's no big deal as long as you have fly screens on your windows. I used to live in a place that didn't (rental house, couldn't do anything about it) and it was really, really annoying having them in the house all the time. I use a fly swat and sometimes those window stickers that kill them if they land on them.
I don't like bug zappers because they kill all bugs indiscriminately and sprays are bad for people and pets as well as bugs.
If you are outside, you can spray around your shoulders with a personal spray from a chemist ect, so they do not pester you.
If at home, make sure all windows have fly screens on them.
Make sure also...and this is the key! that anyone going out the door, or coming in is quick.
No leaving it open even a few seconds...they will get in.
If you don't have a screen door you can buy portable ones now, that attach to your out side door, and cost very little and easy to use.
Great question. Thankfully flies are not an issue in my home. The swatter comes to mind first; otherwise some advanced insect repellant that does not smell your house out, of which works like a diffuser or similar.
My son recently rang me to tell me of a friendly fly that joins him each morning and spends the whole day with him at a remote town in the Northern Territory. I've just posted him two fly veils. He is so desperate that he will ignore any strange looks he receives from his fellow workers. They will probably just be jealous.
Fly veils are not generally noticed in the bush, but I wouldn't walk around the Sydney Opera House wearing one.
Use a Spider & Insect Vac, or a Katcha Bug. You wait until the fly wants to go outside again usually within 2 minutes of being indoors and it will fly towards the door/windows, then vac it in or trap it using one of the two products above. You'll have no mess to clean up either. Both available from www.selectipaustralia.com.au Also great for spiders/bugs/mosquitoes etc
Dealing with Flies in summer.
Make sure doors and windows are kept closed or screens are used.
Use a small burst of fly spray late at night and early in the morning.
All food is covered when not placed in fridge.
Swatter's are used as a last resort.