A great addition to the already awesome tips here is having room mates. You're never too old to shack up with friends or family and save. It's only logical, it cuts down on waste, and makes you grow to be a better person and communicator in adulthood, something the world could always use more of.
it's become very normal for people to live with their parents well into their 20s until they've completed their apprenticeship around hamburg, can't speak for any other places though.