[metalshark]

decreasing belt leach is easy as lightening up a load. alternators are a must for a more efficient engine, but you can still make lighter pulleys at a machine shop even underdrive pulleys.
aluminum instead of steel always works better (depending on the car)

lighter pulleys is a lighter load on the belt.
whether a/c is on or off it will always draw from your engines power same with power steering. (always an option to remove a/c and p/s)

or you can go all out an start putting panels all over your car. might as well just convert it to electric.