Different org's have their own practices. Depending upon on how you plan to repurpose it, the process differs.
Either you can simply keep the network settings (mgmt, vlan, interfaces, gateway etc etc settings) intact & just delete the configuration (bigip.conf) or load a dummy config file. Or if you have no plans to reuse it for now, you can simply go with default factory reset - https://support.f5.com/csp/article/K13127
And then when you intend to reuse it, you can follow your own onboarding process. There is no hard and fast rule on this.
Thanks JaiKumar for replying.
So when we restore it default setting then i can see we will have management access. But account password will be removed. So post that will be able to login with default username and password ?