From the National Lawyer's Guild Legal Observor Manual - yes the guys in the green hats:
If People Are Arrested
At the site of arrest you should ask the police where arrested people are being taken. If
directed to do so by the Legal Observer Coordinator or local Law Collective, go to the
appropriate precinct and talk to the desk Sergeant, ask about charges and when protestors
will be released, advocating for their earliest release.
Legal Observers witnessing arrests should get the arrestee’s name and as many names
and phone numbers as fast as possible from surrounding witnesses. Deal with addresses
and statements at a later time if need be. Encourage the arrestee and friends to shout out
the arrestee’s name or affinity alias if the group has decided to practice legal solidarity.
This is very important as law enforcement has sometimes denied access to arrested
activists if we cannot provide a name.
Ask to talk to the arrested protestors in the van and/or at the police station and tell them
not to say anything except “I want to talk to a lawyer,” and explain that the team lawyers
can answer detailed questions later. Make sure the legal team, or attorneys on call, or
legal aid, or someone, knows about the arrests. (p. 6-7)
http://www.nlg.org/resources/legal-observing