While some people are great at managing their finances, there are many who struggle to budget effectively.
Here are some simple budgeting techniques:
Know your expenses- write down your regular ongoing expenses; everything from mortgage or rent payments, electricity/gas costs, water costs, phone & internet & don't forget recreation & holidays.
Build a budget - there are plenty of websites & apps to access or use an Excel spreadheet but you can go old school & write it out. It has to show income & then all your expenses. If your budget isn't balancing relative to your income then you can see where cuts may need to be made - sometimes you do need to be brutal, especially if you are struggling financially
Employ different transaction buckets - if you know you are prone to spending money if you see it sitting in your account then perhaps having multiple accounts (check for fees & charges) is for you eg. you can set up accounts for bills, socialising & savings. You then place only the funds in the account that you are prepared to spend - this can effectively stop you from spending more than allocated eg socialising, especially if the account doesn't have an EFTPOS card so you can't easily access funds from an ATM.
However you decide to run your budget at least trying to stay within your budget is certainly better than no budget at all.
ASIC's Money Smart website has a useful budget planner & tips: