Use one of the readily available forecasts of the economy versus trying to develop your own economic forecasting model. Most major industries are forecaster by the government, think tanks, and/or industry trade groups. Use their information for your forecast of the industry. For the company, use historical sales data and perform regression analysis. Regression analysis for most publicly held companies will provide strong R squared and R values to be used in forecasting future sales. In those cases where R squared and R values are too low for forecasting purposes, you will have to develop your own methodology to forecast sales. Be sure and explain how you arrive at a forecaster sales value.
