1- Upgrading your dishes - You can get more coins by upgrading your dishes at the store. Each upgrade will increase the price of a dish.
2- Serve the customers ASAP - Your customers' patience level plays an important role. A customer with a high patience bar will leave a bigger tip for fast service.
3- By upgrading your interior you can increase the tips your customers will leave.
4- By using the "Coin Doubler" booster.