personally i like to use about a gram pr cigarette, you do waste more hash, but it personally feels like to me that it produces a clearer high when smoking half a joint with 1 gram of hash, instead of a whole joing with ½ a gram.
i dont know if there's any scientific reason for this, or if the whole experience of better taste, slower burning, and the extra time i put into making it simply makes me enjoy it more.
(disclaimer, it completely depends which hash is being used, for some of the best hash ive smoked 0.2-0.5 grams pr joint is closing in on being too strong to smoke, and will get me absolutely smashed, even if i just smoke half of it, while with some of the weaker hash, i can enjoy a joint with 2 grams pr cig)