|This small glass spice jar from Penzey's makes a perfect fruit fly trap.|
I try as hard as possible to keep everything as clean and tidy as possible, but it is just not practical to never have a single dirty dish in the sink or a ripe tomato on the counter.
One thing I've found that helps is to set traps in every room where they've been spotted. I use empty spice jars that have holes in the lid that are big enough for the pests to fly through, but not too easy for them to just fly right out again.
Fill the jar with about 1/2 inch of cider vinegar and then add one drop of dish soap. Gently swirl it around a bit so the dish soap covers the entire top of the cider vinegar. The fruit flies will be attracted to the scent of the cider vinegar, and the soap will break the surface tension making it impossible for them to stay up on top of it. Thus when they attempt to drink the cider vinegar, those buggers will drown!