The best time to sell more is when your client just bought something from you.
After completing a low price purchase (that just qualifies them as a buyer), don’t leave the high priced item to an online upsell option. Instead call them immediately, ask them a few qualifying questions and do a whole upsell process (that you can control much better) over the phone (compared to an online simple buy option.)
Customers don’t want to be bothered, and unless you have the right sales people doing it the right way, you are better off not bothering them until the right time.
Have “get help” button at many places in your store. The shopper should not walk more than a couple of steps to get to such a button. At the same time have no sales people visible at all. When the client presses such a button, a sales person should know where it was pressed and be there in a couple of minutes.
If you are not in a rush to get to the high-level decision maker, you might want to make them call you.
Create an automation sequence specifically for them. Include emails, snail mail, couriers, as delivery mechanisms. The main point is to make this long and intensive and always to be creative in having a reason and a benefit for them to receive your communications. Each communication should have one call to action: call me.
It’s noisy on the beach, and you want to call your kids back (you want to go home, or they have gone too far in the water, etc.)
Have a wristband that strongly vibrates when you “call it” using a phone app or a dedicated transmitter “button.”