Turn the WiFi off when you're not using it.
Don't eat meat (not everyone can do this, but it worked for me at uni!)
Supermarket brands for things
Don't drink
Create different budgets for your weakness. Food budget, bills budget, then if you know your weakness is take away, or wine, have a take away or wine budget and stick to it. Gradually cut down the weakness budgets.
Stick on the 'save the change' feature with your debit card.
Meditate, write on paper, or exercise when you're bored, to save money.
Stick the heating on overnight and you'll wake up so hot and stuffy the next day, you won't want it on for a good few days. Or go and stay with someone you know who is tighter than you are with the heating and has a cold house. You'll come home thinking your house is boiling.