I am a PhD student, and I live on about 60% or 70% of my scholarship (though my parents do still pay for e.g. my car insurance; if I also counted all the money my parents spend on me, it'd be higher, but probably still not close to 100% unless I'm forgetting lots of stuff). I picked “about 75%”.
(EDIT: Just noticed that the poll said “need to” -- well, I could in principle reduce my expenditures, but it wouldn't be anywhere near trivially easy for me to do so by a substantial amount.)
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.