Pick a small public company (market cap under $1 billion) with a simple business that you find interesting. You could pick a larger company, but the exercise may be a bit more difficult.
Go to Edgar, and pull down the income statement and balance sheet from the company’s latest 10Q or 10k. (It might be easier with a 10Q).
Make sure that the balance sheets you use correspond to the period of the income statement.
The balance sheet will show a snapshot from the beginning and end of the quarter. For each line on the balance sheet, calculate the change between the between the beginning and the end of the quarter and determine if that change was a source or use of cash.
Use that to see if you can explain the actual change in cash. In the above example, cash changed by 30.8 million. The statement is internally consistent because the total sources less the other uses foots to that 30.8 million.
Try to classify the changes between Operations, Investing, and Financing. You will probably not be able get the dollar amounts to match with the numbers publicly reported on the cash flow statement, but show the variance to the publicly reported totals for Cash from Operations, Cash from Investing, and Cash from Financing.