1. Understand the concept of common size analysis: Common size analysis is a technique used to compare financial statements by expressing all items as a percentage of a common base.

2. Choose the financial statement to analyze: Common size analysis can be applied to both balance sheets and income statements. Choose the statement that is most relevant to your analysis.

3. Calculate the percentages: For each item on the financial statement, divide the item by the total of the statement and multiply by 100 to get the percentage.

4. Compare the percentages: Compare the percentages across different periods or companies to identify trends and patterns.

5. Interpret the results: Analyze the results to identify strengths, weaknesses, and areas for improvement. For example, if the percentage of cost of goods sold is increasing, it may indicate a need to review the pricing strategy.

6. Use common size analysis in conjunction with other financial analysis techniques: Common size analysis is just one tool in the financial analysis toolkit. Use it in conjunction with other techniques such as ratio analysis and trend analysis to gain a more complete understanding of the financial performance of a company.