Using a coating with a refractive index between that of glass and air. For example, for a lens coating with n = 1.25, the Fresnel equation tells us that: Rair-coating = 0.0123 and Rcoating-glass = 0.0083. The total reflection is ~2% or about half that of the uncoated surface.
Astute readers might ask, “Then why not keep adding layers with a refractive index between that of the materials on either side?”
In theory it is possible to reduce reflection in this way (see Moth Eye Technology below) using multiple layers such that n increases step-wise from the air to the lens. One limitation is in developing coatings of the required refractive index. E.g. there is no coating with n = 1.25 (which is near the optimum value for a single coating on glass) the closest is probably MgF2 with n = 1.38.
If light reflected from the lens surface is exactly out of phase with light reflected from a lens coating, the two cancel each other and there is no reflection (assuming equal intensity).
The condition for destructive interference is met when the coating thickness is 1/4 of the light wavelength for a specific wavelength at a specific angle of incidence.
In practise, multiple layers are used to address different wavelength regions and give broadband anti-reflection. AR coatings typically reduce reflectivity to ~0.4% over the visible region. Ten optical surfaces, each coated to give 0.4% reflection loss, equates to a total transmission of (0.996)10 = 96.1%; considerably better than the 66.5% transmission with no coating.