After the final whistle.
If I am NAR I go and get the spare ball nearest me if there is one then...
Round my way I (or we) go to the half way line at the edge of the centre circle, facing the crowd (if there is a crowd on one side) or facing the benches if there are no punters. Ref in the middle, AR1 to the left, AR to the right.
We then stand politely - no silly body language, no loud comments, flags rolled. The teams come either side of the circle, typically captains take turns leading a quick clap/chant then there is a queue to shake hands. At the higher levels the handshake is more organised and one team goes first. At lower levels they all want off sharpish but normally all the players will shake at least with each other.
We can tell if we've had a blinder at lower levels at because every single player will wait/queue to shake with us. This happened in one out of two futsal games yesterday - not a bad percentage - considering there was a debated DOGSO RC
After that, follow the players off to the changing rooms, if available. If the game has involved heated incidents and the players are still arguing - on these rare occasions you may want to stay within earshot or with a view of the players until they are tucked away and getting changed. Same outside - if they are getting changed at the touchline, if there has been aggro you may want to wait until the players have left the playing area.
...and yes, if with ARs, of course, thanks, feedback, comments