Use only PURE SILICONE spray or TEFLON spray!     DO NOT USE WD40Ò or any oil or petroleum based products. These will make a gummy mess and attract even more dirt to the parts. Pure silicone will not allow dirt to stick to itself and will not stain most painted walls as you spray it on. It’s a good idea to protect curtains, wallpaper, and window treatments. Put the spray can close to the track or channel the sash moves in. This is very important for sideways sliding windows that don't use rollers but have nylon glides on the bottom. Once that glide wears through, the window track can be seriously damaged. Operate the window several times to see if it's better. If not, spray once again. On windows you use most frequently, this  lubricating and cleaning may need to be done more often,. perhaps 2-3 times a season. The window came lubricated from the factory but with time, this wears off and needs to be done by the homeowner. Pure silicone spray may be purchased at hardware stores or at lumber yards.