The client's decision
First, establish what the client needs to decide. A request to improve profit needs a time period and an agreed measure of profit. Ask how much improvement the client wants, which geography is in scope and what constraints apply. If the target is a $1 million improvement this year, distinguish actions that can produce results this year from investments that take longer.
The profit calculation
For a single product, operating profit equals units sold multiplied by the difference between price and variable cost per unit, less fixed costs. Each part gives you something to investigate. You can ask whether volume has fallen, contribution per unit has changed or fixed costs have increased. For several products or routes, calculate each contribution before subtracting the relevant fixed costs. Write units beside the numbers so you compare annual revenue with annual costs.
A structure that fits the business
For an airline, passenger volume can be split into seats offered and the share occupied. Revenue per passenger may include the ticket and ancillary purchases. An online retailer needs a different volume breakdown, such as visits multiplied by conversion and items per order. Explain why your branches fit the client before requesting data.
Your first investigation
Explain your working hypothesis and what evidence could change it. Falling airline profit might result from fewer passengers or a lower contribution per passenger. Comparing both with last year shows how much each change contributes to the decline. Start with the larger driver, but keep the other explanations available.
Using the result
Suppose a loss-making route earns more contribution than the costs that would disappear if it closed. Closing that route would reduce total profit. You need to distinguish costs the business can avoid from costs it would retain. When recommending an action, explain which calculation supports it and which assumption still needs checking.
Your structure should help you choose the next calculation that could change the client's decision.