Sort your expenses
It seems simple enough, figure out what everything costs, throw it on a piece of paper and make sure you have enough money to pay for everything on the list. It isn't complicated and that is literally all you need to do but I find there are things that everyone forgets and don't always calculate properly.
These things are a nightmare. They happen every year and you never know how many you need to fork out for. If you have kids the problem gets even worse because kids have birthday parties for other kids. Tip: It's not a great one but go above and beyond what you think you could need. I allow money for my kids, kids friend's, family, extended family and Christmas. Once we had worked this out we actually had a full conversation with the older family members and agreed on a Secret Santa undertaking for Christmas and we combined a couple of birthday dinners into a date in the middle so the costs were kept down.
These get tough because chances are you don't know what amount you're going to receive until you've received it. Over estimate it, once you have a monthly number multiply it by 12 and then divide it by 52 if you're paid weekly or 26 if you're paid fortnightly. Anything left over after a year you have free reign over but chances are there will be incidental expenses you weren't expecting because life happens.
Do you have Netflix, Spotify, Outdoor Living Magazine subscription? They may only cost a small amount but between Netflix and Spotify you're paying roughly $25 a month or $300 a year. Add in expenses on iTunes or the Play Store and a daily coffee and the little numbers are coming for you in a bigger way.
Managing money gets hard when you have a lot happening so what I do is I have 7 different bank accounts. You'll find most banks offer fee free accounts when you deposit a certain amount of money into the account each month. I have separate accounts for Everyday Spending (keycard linked), the business, Loan Repayments and Direct Debits. These all get over $1000 a month in them either through salary deposits or money being transferred into them from another account. 3 of them are offset accounts also. Then I have separate accounts for Bills, Car Expenses and Birthdays. These are no frills accounts that have no fees regardless of the amount deposited but can't be offset accounts or have a keycard attached. They're all visible on my internet banking and keep our finances incredibly organised. If there's an issue you can pick it really quickly also as the account shows it.
I use an excel spreadsheet to see what everything looks like and have what accounts each expense needs to go to so that everything is in check. I also have an incredible wife that has this down pat and I don't look at the bank accounts until I go to pay for petrol and the keycard is empty... Happens at least once a month. Before we used multiple bank accounts though we used 7 different envelopes and had cash in each for whatever needed to be paid. This was before Bpay though and you went to a Post Office to pay your bills.