Most forms of payment are just fine. Can be right after the service is provided. Or can be a pre-pay. Whatever is convenient for you.
Online payments can be easily setup with an emailed link, and a payment portal is being set up now.
Card by phone call works.
Some clients prefer to have a card kept on file securely.
In-person, while less preferred during the covid-19 times and moving forward is fine, and handled appropriately (safely). There is a contact-less card/device reader here.
Venmo, PayPal ok too. Want something else? Just ask, all good.