Who is it for?
What are the symptoms?
How long have the symptoms been present?
Action already taken?
You don’t have to ask these questions in order, and a customer might give some of this information without you asking.
As long as you get these into the conversation, you should be able to find out enough information to make a recommendation. The golden rule is: if in doubt, refer to the pharmacist. Don’t be embarrassed to ask for their advice as they have a lot of additional information about products and symptoms to hand.