I have many uses for WD-40 but bought this primarily to spray on my lawnmower blades after each mowing.  First, I clean off the blades with a hose and wipe off the dirt, then I give a good spray on the edges of the blades to help prevent corrosion and keep the blades sharp.  Once it's sprayed on, I just leave it wet, don't remove the WD-40 or wipe it down.  I've heard it's good to spray along baseboards and outside the house along the foundation to repel insects but I didn't really have an insect problem anyway so I'm not sure it's the reason I'm pretty much insect free in the house.  I also use it in the winter on snow shovels  and my snowblower chute to keep the wet snow from sticking.  Cooking spray works well for that too but this is a review of WD-40.