Have a second supplier for anything you can't trade without

Make a list of everything your business can't operate without for a week: key stock, packaging, couriers, your payment provider, even your accountant. For each one, find a backup before you need it. Open an account, place a small order, and check prices and lead times. You don't have to use them regularly, but when your main supplier has a shortage, a price rise or goes bust, you can switch in days, not weeks. It also puts you in a stronger position when you negotiate with your main supplier.