After you have track your spending for a month, you now have the information you need to create a monthly budget. Now you know exactly how and what you spend your money on. If you did not have a surplus of money at the end of the month, you can now see area where you can trim your spending in order to operate you budget with a surplus next month.
I'm a fan of MS Excel _ my apologies for those who have issues with Microsoft _ because I find its powerful calculations are easy to manipulate to help me better understand my finances. It doesn't really matter though which spreadsheeting package you use so long as you are able to calculate your amounts effectively. There are commercial budgeting worksheets available but if you want to create your own its a simple process.