I personally use an app called “Wally”, which is a daily expense tracker. So, every time I spend some money, or my credit card is charged, I just whip out the app, and make a quick note. It takes less than 5 seconds to record my spending, and I ensure that every single purchase is noted – not matter how small. After a couple of days, recording this becomes second-nature. And the end of the calendar month, you can go back and see where you’ve spent the most amount of money.