From my experience as a business person, in buying and selling, I have discovered some helpful tips on how to increase profit. I an happy to share some in this forum.
Customer relation, a business person must understand that customer is king and should be treated like a royalty. Even it they are buying the least thing in your shop. When they leave your shop delighted, be assured that they will always come back to patronise you. And they will even market your products to their friends. Meaning more patronage for your business which will be increasing your profit.
Your business should have at least one season when you give out rewards and discounts to customers when they buy your products. This will increase your sales geometrically and when you remove the cost of the reward and discounts, you will still have increased profit.
Stock different brands of the products that you sell. Customers will prefer to enter a shop where they will see different varieties of what they need. More customers will enter and will even be tempted to buy more than they planned for. More customers equals more profit.

Please feel free to drop your own ideas on how to increase profit in businesses.