Methods of treating a wellbore comprise displacing a drilling fluid comprising an organophilic clay treated with a quaternary ammonium surfactant having an amide linkage into the wellbore. Methods of drilling a wellbore comprise: applying torque to a bit within the wellbore and concurrently applying force to urge the bit to extend through the wellbore; and circulating a drilling fluid past the bit to remove cuttings therefrom, the drilling fluid comprising an organophilic clay treated with a quaternary ammonium surfactant having an amide linkage. Methods of preparing a drilling fluid comprise: forming an organophilic clay treated with a quaternary ammonium surfactant having an amide linkage; and combining the organophilic clay with an oil-based fluid.