This paper addresses the challenge of correcting astronomical data for the wavelength-dependent effects of Galactic interstellar extinction. It reviews the general features of extinction from the infrared to the ultraviolet, including spatial variations, and highlights the wide range of extinction properties found in the Galaxy, particularly in the UV spectral region. The paper discusses constraints on the wavelength dependence of extinction and correlations between extinction curve shape and interstellar environment, which provide guidance for correcting data. Several strategies for dereddening are presented, along with estimates of the uncertainties associated with each method. A new derivation of the wavelength dependence of an average Galactic extinction curve from the IR through the UV is presented, along with an estimate of how this extinction law varies with the parameter \( R \equiv A(V)/E(B-V) \). These curves are suitable for dereddening IR-UV spectrophotometric data and can be used to derive extinction relationships for any photometry system. The paper also discusses the uncertainties in dereddening, including those related to the measurement of \( E(B-V) \) and the choice of extinction curve. Finally, the paper addresses the correction of data for extragalactic extinction and the wavelength range 912-1150 Å, where the far-UV rise continues.This paper addresses the challenge of correcting astronomical data for the wavelength-dependent effects of Galactic interstellar extinction. It reviews the general features of extinction from the infrared to the ultraviolet, including spatial variations, and highlights the wide range of extinction properties found in the Galaxy, particularly in the UV spectral region. The paper discusses constraints on the wavelength dependence of extinction and correlations between extinction curve shape and interstellar environment, which provide guidance for correcting data. Several strategies for dereddening are presented, along with estimates of the uncertainties associated with each method. A new derivation of the wavelength dependence of an average Galactic extinction curve from the IR through the UV is presented, along with an estimate of how this extinction law varies with the parameter \( R \equiv A(V)/E(B-V) \). These curves are suitable for dereddening IR-UV spectrophotometric data and can be used to derive extinction relationships for any photometry system. The paper also discusses the uncertainties in dereddening, including those related to the measurement of \( E(B-V) \) and the choice of extinction curve. Finally, the paper addresses the correction of data for extragalactic extinction and the wavelength range 912-1150 Å, where the far-UV rise continues.