If you are experienced with spreadsheets you can also add extra features such as the ability to create graphs from the data you entered. Graphs make it easy to get a quick view of your current financial situation. The graphs will allow you to easily spot trends and areas that are in need of attention in order to keep you on budget.
I think it is best to keep a monthly budget instead of an annual one. This is because things change monthly. You might need to spend extra money for a holiday party in November and December, and so forth. So we are going to make a monthly budget. However, what you need to do is first consider all of your yearly bills. These are bills that you pay once a year only.