You might spend more on "wants" than you think. A threadbare minimum of warm clothing is a need. Anything beyond that, such as shopping for clothes at the mall rather than at a discount outlet, qualifies as a want. Yes, the rules are tricky, but if you think about it, they make sense.
How to use your monthly budget worksheet. Below is a worksheet that attempts to list possible sources of monthly income as well as expenses. As everyone's financial situation is different, you may find that not every category is applicable to your income or spending. You may even find that some months are different than others, but you should find through going through this exercise you are better prepared for those changes and even accounting for unanticipated expenses.