A lot of differences according your situation. HF only or CPDLC ?
In NAT you can refer to
this doc, where specific procedures are described.
Bigger problem when HF only... no way to talk with them and... huge CB closer and closer
Some times you may need to deviate and/or climb ralating on TCAS only and... all lights on ! Of course communicating via 121.500 and dedicated air/air frequencies to all other listening traffic(s).