Isn't there three ways, downshifting, shutting down cylinders and exhaust restriction? Also Telma (Electrical) and Retarter (hydraulic) helping brakes should not be forgotten. Engine braking a car is very nice to save both gas and brakes, just not overdo it like I did. I have to replace my front rotors because they are so rusted on the back side that my car didn't pass inspection, apparently there is such a thing as using your brakes too little.
In my experience you only feather the clutch when starting or downshifting without revmatching, when driving it's actually best to think of the clutch as a digital switch. I still remember when I was in the military and was taking truck driving lessons and the driving intructor shouted to me: "WTF are you doing!?! it's nothing to be thinking about, just let it go" The reason for this is pretty simple: less friction time to wear down the clutch. Just remember this, mess this up when downshifting and you may damage your transmission, so this is not for inexperienced stickshift drivers.
To get the best milage you have to think about whats burning up fuel unnecessary: Basicly breaking down to later accelerate, ideling and shifting.
To get the best milage on a highway with a engine @ working temperature gently accelerate to 6k RPM in the first gear and then go directly to 5th and leave it there as long as the engine runs smoothly, in my MSP that's around 2k RPM on a straight road. Just remember that as soon as the engine bogs down it dumps fuel into the engine to keep it going and this affects the gas milage, so downshift in time. Going 35 mph I usually use 4th even though 5th is possible. When meeting a red light I find it best to keep it in gear down to around 1500 RPM and then shifting into neutral whithout using the clutch at all, manual transmissions are designed for this and this method will save both gas and clutch wear.
But especially in the US where gas is so cheap, my advice is to just go ahead and get to know the car and try to remember what RPM ranges the car will run at in different gears before trying hard to get hypermilage. The Proteges aren't exactly hypermilage cars anyways, with my MSP I mostly get 30-34mpg on slow highways myself (where my 96 Hyundai Elantra wagon beater car I can get 40, and with my parent's diesel car 55mpg is achievable.)