Reprinted from BrightNest.com
Window tracks are good at two things: Making it possible to open a window and collecting insect corpses. It's a nasty reality, and it'll gross people out if they see it. Here’s an easy way to clean up the dirt and insect... stuff from your window sills.
1. Pre-clean with a vacuum (optional).
If your tracks are looking really bad, give them a once over with a vacuum attachment so you don't use a bajillion Q-tips in step two.
2. Dip the Q-tip in vinegar and run it along the nooks and crannies of your window tracks.
Depending on how big your windows are (and how many windows you're cleaning today) you may need a bunch of Q-tips and a few fresh shot glasses. You want to have enough vinegar on the Q-tip so that it's kinda "runny" when you start cleaning each track.
Tip: If your tracks are really gross and sticky (as in, this-is-the-first-time-you've-ever-cleaned-them, sticky) an old toothbrush might work better here.
3. Use the paper towels to mop up the vinegar and additional dirt and insect graves.
You can press the back of your finger against the towel as you "mop" up the vinegar. If your tracks are too narrow for a finger, try using one of those nasty Q-tips.
4. Schedule another round in 3-6 months!
All done? Schedule this to-do for 3-6 months from now (depending on how fastidious you are).