You can find the inventory methods used by the companies in your industry whose stock is publicly traded by reading the Summary of Significant Accounting Policies contained in each company's Form 10-K. The Form 10-K is the annual report to the Securities and Exchange Commission or SEC.
The Summary of Significant Accounting Policies will appear as the first or second item in the Notes to the Financial Statements.
Most publicly traded corporations will have an Investors Relations link at the bottom of their website's home page. On the Investors Relations page you will find a link to the corporation's SEC filings.