Payments made be made via Paypal. Those with a U.S. bank account may also send checks if preferable. Good, old-fashioned cash is fine as well for any in-person sessions.
In this day and age, I must ask, too, that you please immediately report to me and to the authorities any suspicious requests for money for services not rendered or any fake pleas to send money that seem to be sent by hackers. I will never ask you for your credit-card information as I now only use Paypal for security.