So let's just say despite being a perfect housekeeper you happen to have a little fruit fly problem (after all sometimes you just can't help but end up with a few with all the fresh fruit and veggies) 

Also, in case you didn't know this fruit flies can breed in your drains, so if you have a problem and it doesn't seem to be getting any better clean your drains.  Use baking soda and vinegar: put two tablespoons down the drain, and then pour in an equal amount of vinegar.  Place a snug fitting plug in the drain and let sit for about 5 minutes.  Note: if you have a double sink you will need to block both drains.  Run a bunch of hot water down the drain to stop the reaction and flush out the loosened debris.  Repeat if you suspect it is still gunky down there.  Of course, you can also use something stronger ;-)

To make a fruit fly trap you need an envelope, a cup, scissors and tape OR an elastic. 


Now you have a use for those annoying junk mail envelopes.




Put the envelope in the cup so you can judge where to cut, you want between 1" and 2" of overhang.




Cut a curved line to make a cone




Cut a small hole in the bottom, about 1/4"




Place the paper cone in the cup and gently fold over the overhang




Bait the trap with whatever your fruit flies like.  I find a little water in the bottom helps attract the flies and prevent the fruit from drying out.




Please the cone back on the cup and secure with tape or an elastic.



The fruit flies will go in and be unable to find their way out (stupid fruit flies).  You can either take the trap outside and release the fruit flies then reuse the trap.  Or if you don't want to deal with it, chuck the whole thing in the trash.  It is best to clean out/replace the trap every day or two.  If you leave it longer than two days you end up with little fruit fly maggots..... yuck.

Hope this was helpful.