Sales forecasts: how to improve accuracy while simplifying models?

Identify the top four metrics that drive sales among the metrics that I have suggested in this article (by all means, please do not ignore external data sources - including a sentiment analysis index by product, that is, what your customers write about your products on Twitter), and create a simple regression model. You could get it done with Excel (use the data analysis plug-in or the linest functions) and get better forecasts than using a much more sophisticated model based only on internal data coming from just one of your many silos. Get confidence intervals for your sales forecasts: more about this in a few days; I will provide a very simple, model-free, data-driven solution to compute confidence intervals.