You can read The First Protocol on the SETI Institute site, but we broke down the nine-item list in more easily digestible terms here:
If you think you've received a signal from aliens, double check. Like, quadruple check. The most plausible explanation for whatever you've discovered has got to be extraterrestrial intelligence. If it's not, go back to the drawing board.
So you think it's aliens, huh? Pump the brakes. Only tell your fellow researchers and observers so they can independently confirm what you think you've found.
Wow, congrats, it really is aliens! Tell more researchers and scientists, specifically through the Central Bureau for Astronomical Telegrams of the International Astronomical Union. Surely you have them on speed dial. The IAA has a lengthy list of some other international institutions you should give the scoop to now.
Here we go. TELL. EVERYONE. Do it promptly. But why the heck would anyone want to wait?!
Time to show the receipts. Make sure all of your data is available to the international scientific community through publications, meetings, conferences, etc. FaceTime scientists on the other side of the globe to show them your happy tears.
Lock it down. Permanently record and store your evidence to the greatest extent possible. This is your legacy, for goodness sake, back it up!
If your evidence of alien detection is in the form of electromagnetic signals, you're going to need to talk to some people at the International Telecommunication Union to protect it.
Hold up, you're trying to send a message back to the aliens?! That's how intergalactic armageddon gets started! There's a whole different conversation that needs to happen before we dive into that.
The SETI Committee of the IAA will keep an eye on your discovery for the rest of time. Don't go tryin' anything funny on us, aliens.