Wax is an excellent and cheap solid lubricant. Paraffin wax, the most common wax used in candles the world over, is also used in a variety of applications such as ski and snowboard wax to help reduce friction. Any chunk of wax will do for your project, but two particular shapes are best suited for particular tasks: Tea light candles are a perfect little size for doors and window frames, and taper candles work great for windows and doors with tracks like a sliding glass door. A white candle is best, even if the surface is a dark wood, because you don’t want to add any color into the mix and the white wax will be spread so thin it won’t be noticeable.
Try silicone spray lubricant.
WD40 works too. Just spray it around the opening of the window frame.
This technique works for all types of windows. Don’t forget to spray the hinges. It will make your life a better place.
If it squeaks - spray it!
Tip: Try this on doors too! (^_^)