No ... no ... no!!!
Yes, to slipping it out of gear & coast down hills but never, ever, ever, never, ever ride the clutch. Every penny of fuel you save will be lost in an early clutch replacement/rebuild. Coasting down hills with the clutch depressed will cause the early demise of the throw-out bearing. Driving with your foot resting on the clutch (but not depressed) will also cause additional wear on the throw-out bearing but will also cause wear (& early demise) of the pressure plate.
Sorry to be so emphatic but it's a sensitive issue with me after teaching 6 kids to drive.
Similar issue with resting your foot on the brake whilst driving. Even light pressure will engage the brakes a little causing extra wear & killing mpg.