I don't like to spray anything in my apartment since it's so small, so here are some tips that will help keep the bugs out of your apartment in the first place.  

One Door at a Time - I know this sounds like a no-brainer, but here in Korea there are usually two sets of doors coming into the apartment.  One from the hallway to the area for your shoes, and another coming into the apartment - and keeping them closed is key.  Obviously, keeping the doors shut will keep bugs out.  But when you do leave or come home, try to do one door at a time.  Why?  If a mosquito happens to fly in when you are coming home and you just push the other door open, it'll just fly in and wait until bedtime to bother you.  Keeping one door shut will give you a chance to do a quick check for any flies or mosquitoes before going into your apartment.  Squashing a mosquito in a small area is much easier than chasing it around your apartment, looking into all the nook and crannies and under all the desks.  

Keep Your Kitchenette CLEAN - that means the cupboards, the counter and the sink.  If you let food sit anywhere in the open, even crumbs, flies and cockroaches will just show up.  During the moist or warm months when bugs are out, try to keep everything clean and wiped down.  Also, stagnant water will attract these little flies.  Kind of like a swamp.  For me, the plastic thing under where I put my wet dishes holds water and when it dries it's kind of funky.  Flies love this stuff.  Also, don't throw perishables away where they are in the open.  Get an airtight container and store it in the fridge otherwise it will attract tons of flies.  This happened to me my first month, so I quickly got the container and it stopped completely.  In any event, keep your kitchenette clean and this will keep the bugs away.

Check the Screen on Your Window - Screens.  If you see one, that means no mosquitoes, right?  Not in my case.  I have nice, new windows and screens but somehow mosquitoes were still getting in. When the weather is nice I like to keep my window open (with the screen shut) to enjoy some fresh air.  As I looked closer though, I noticed these small openings at the bottom of the screens.  These small arches are about the size of a half of a dime.  It's most likely there to let water drain out when it rains, but it's also a doorway for bugs if your window is open.  To solve this problem I took a piece of folded tissue and stuffed up the hole and it solved the problem.  There are still some of the tiny flies that actually crawl through the bristles on the edge, but you can't have everything!

Turn on the Bathroom Fan - I noticed some flies on a couple occasions sitting around the fan in my bathroom.  As I looked up I noticed that the vent has no screen.  It's just the bars that block anything large from coming through.  I could see the flies were easily coming through.  So whenever I was home I turned it on so they couldn't come through.  I actually turn on my fan at times for background noise so I can fall asleep so it was no big deal for me to keep it on at night.  During muggy nights, it may not hurt to turn the fan on to vent out any bugs trying to buzz in.

Of course you can use the fogging products to chase them away, but I prefer not to.  I'm not sure they really work all that well anyway.  When I first moved here I used one that the previous teacher had.  It didn't seem to have any impact on the mosquitoes though.  They just buzzed around as usual.  I think I heard them laughing at me once!

I think the best defense is to keep them out in the first place.