I just found out about this today and want to try it later but what's the expected etiquette? After you and your group kill the guardian and a new rift is opened, does everyone leave?
Runners
Clear up to guardian or close to it. You can damage the guardian if you want but this is unnecessary unless you're running T5/6 and worried about ability of leechers. Note that damaging guardian on lower torments might be a bad idea because a leecher might spawn in and accidentally kill it before other people can get a chance to get loot.
Broadcast that you have guardian. An example that has worked well for me is "T# guardian - X spots open - need opener".
One thing you can do to get instant opens is say something like "first to open gets invite to next rift" or "first/last to join opens" or "highest paragon opens". Setting this up prevents the standoff that happens after rift is closed since someone is 100% responsible.
You
can run rifts w/ people and get openers. I find duo is the best but running in groups of 3 is also possible. If you do this people will always open immediately but your broadcast should be something like "T# guardian - 1 spot - must open" so that they are clear on what they're getting into. when you do this I've found it is helpful if you get someone that opens to msg them and ask if they want to get invited to the next one. Now you got a leecher that you know will open your rift for your party.
TIP: If people leave or seem like they HIDE too much block communications with them and they can't request invites from you anymore. I'll often decline invites from people if they've joined too many of my games w/o opening to give other people a chance.
TIP: If the guardian spawns on a good map like prison or cemetery I always clear around the guardian before inviting. You can also ask people that are going to open if they want to clear a good map after they kill guardian before they open. Usually people are OK with this.
Leecher
You want to join the multirift community as well as RIF to leech. I don't like multirift for running because opening the next portal is
implied not a requirement (although it seems like people mostly open anyway).
BE PREPARED TO OPEN. If you don't have any keys don't join games, period.
Basically you want to watch chat and hover over the last line w/ names. Wait for someone to call out and right click then REQ inv. If you notice the option shows up but goes grey real fast it's a glitch in the UI. This means they're busy so that they can't get requests. In this case click their name and just say "invite please". I've found that getting invites into multirift is way easier.
Etiquette inside rift:
Port to party leader
Wait for everyone to load into the rift
Kill guardian
Let party leader close rift
Wait for countdown to drop down
Open Rift (or let someone open it. I usually open every other rift but it isn't uncommon to open like 5 in a row)
Leave game immediately
For multirift you can ask if they want an open since it is only implied, not required.
NEVER leave a game until portal is open in RIF community, even if someone else says they're going to open.