Find a template that allows you the flexibility to adjust to fit your budget and lifestyle needs. You're probably better off tracking only 9 or 10 budget categories rather than 30 or 40. You can always split it out later if you find you need more granularity into a particular line item.
There are currently two different budget templates, one for a monthly budget and one for an annual budget. Both track your income and expenses and give you some pretty charts and graphs of your cash inflow and outflow using pre-set formulas.
For ultimate simplicity, the Federal Trade Commission published a 2 page fillable PDF that allows you to input your income and expenses by month. You can also print it out and fill it out by hand if you are more comfortable with that.
There are dozens of budget spreadsheet templates available to choose from. Microsoft has something for everyone, whether you're looking for a simple monthly budget tracker or a fancy budget workbook with multiple tabs and graphs.
PearBudget started as a downloadable Excel template that is now a full-blown online budgeting tool. But the original Excel budget spreadsheet is still available to download for free.