How do I do an ACH transfer instantly?

I'm interested in understanding the process of making an ACH transfer instantly. Could you explain in detail the steps involved? Specifically, I'd like to know if there are any special requirements or services that need to be enabled for an instant ACH transfer. Also, are there any fees associated with this type of transfer? Finally, how reliable and secure are instant ACH transfers compared to traditional methods? Your insight would be greatly appreciated.