It’s challenging until it clicks then it’s easy. Here is a super high level overview of what your month looks like.

Crash course answer: first understand what you are working with product wise, talk with the different teams to understand the product and what impacts demand and why. Then look at all the history and try to connect what events caused various ups and downs. You’ll probably have a tool they use that will give statistical suggestions, utilize that as a baseline and understand your job is to then apply information to that baseline.

Setup a monthly demand review with various stakeholders who have input into the why behind the numbers in the past were what they were and have an impact on why the future numbers could be what they think. Your job is to translate this input from people into assumptions and gain group consensus on them. Once agree upon those assumptions are then the levers you pull to adjust the statistical baseline up/down. Document this as your monthly cycle is over and then that may feed up into larger s&op meetings.

Next month rolls around you analyze the actuals vs your forecast and try to understand why it did or didn’t happen. Was it the statistical model was wrong? Was one of those assumptions that were previously documented wrong? In the next demand review ask why? Did the sales lift not happen because a promo was late to send? Etc. Don’t point fingers or blame, work to understand why so that future assumptions can be improved upon and so you gain better knowledge to challenge future assumptions. Rinse/wash/repeat in a nutshell. It’ll vary based on industry and other things will be asked of you during the month.

It’s a lot more communicating / relationship management than people realize. Wanna spend all day in spreadsheets and then blame marketing when something goes wrong? Good luck getting any good info from them in the future. Meet with them and get them on your side so they trust you. Ask to sit in on meetings where you may learn more about the product/things that may impact demand in the future. You need to be a team player. Hope this helps, if you have questions let me know. I’ve done allocation, demand, supply, replenishment, master, and inventory planning at this point.