The most powerful analytical approach I have seen to date

This sounds a little pompous, but it is true. I have used this approach several times in different industries, and in different customer analytics settings, and every time it was huge success. Fortunately, the method is very simple (me like simple!), and can be replicated in a variety of situations.

1. Find a natural break of your total sales into units and dollars (aka rate and volume).
2. Pull the data by various groupings and trend over a few years. Find contribution of each part to the total and trend.
3. Take your volume variable, and repeat steps 1 and 2 again.

Here is an example. Total retail sales by week were broken down by the number of transactions and an average dollar amount per transaction and trended over five years. That of itself was quite a revelation. On the next level, we looked at the number of units per transaction and dollars per unit. Next, we looked at the breakdown of units and dollars per unit by category over time, and then split it into changes due to mix shift, or share of more expensive items that have longer life and lower sales volume, and inflation, or change in price of the same SKU. This was probably the most simple, perfect, insightful, and successful analytical project I lead.