How do I permanently buy a domain name?

Hello there, I'm curious about the process of permanently buying a domain name. Could you please walk me through the steps involved in securing a domain name for good? I'm particularly interested in knowing about the registration process, any associated fees, and whether there are any specific requirements or precautions I should be aware of. Additionally, could you also shed some light on how to renew the domain name in the future to ensure its continued ownership? Thank you in advance for your assistance.