Buy used textbooks and sell your last semester´s book
New books and studying material could sometimes be really expensive, so one way how to save this expense is to buy textbooks from another students who don´t need it anymore, and you should do the same thing with your old textbooks, which would only lay under the layer of dust.
Don´t make impulse purchases
Many times you see something you want to buy immediately, but, let it pass through your head for couple of days. Often after this time happens, that you change your mind, and, voilà you have succesfully saved some money!
Never go grocery shopping when you are hungry
Never! Otherwise you will buy even things you do not normally eat.
Live with flatmates, so you can split rent and utilities
You can cut a big part of spendings each month by splitting utilities between you and your flatmates.
Make your own coffee
While coffee shops are convenient, they charge hefty prices that really add up over time.
Cook your lunch
The same case as with a coffee. It is always better to make your own lunch, it will cost you much less, and, in addition, you will always know what your food consists of.
Walk, use public transportation or ride a bike instead of taking a taxi
Even though some taxi companies have really appealing prices, when you use it repetitively, at the end of the month the total price could make your jaw drop. Moreover, with walk or a bike ride you can add some "exercise" to your day.
Sell what you no longer use or need
Why keep things you no longer use, and occupy the space in your wardrobe when you can pass them to someone else, and at the same time make a money out of it? There are plenty of stores and web sites like Craigslist, Poshmark or Gumtree, where you can sell your used clothes, tech items or furniture.
Shop where they offer student discounts
Search for a shops where they offer discounts to students with a school ID.
Drink water
It is free, and better for you, anyway.