Here's a huge tip for crewmates to catch imposters. In the Y-shaped hallway, if you see someone standing still in the middle don't think they are suspicious for not doing tasks and standing in place. First of all, imposters generally look for kills unless they are trying to gain the trust of other imposters. Second, crewmates like me will stand in the middle to catch imposters venting. On Mira HQ, venting looks like a good option and viable for getting away with kills since you have access to any vent. However, due to the layout of Mira HQ, you can catch people venting even though you never actually saw them. I believe the devs intentionally designed this map to do this because it's the only map with door logs which is a mechanic I love and find much more useful than cam/security (but opinions vary among others). To catch an imposter venting, stand in the middle of the triangle or near it and remember who past you when, where, and keep track of where everyone is. Generally, only do this when the game just started or at the end of a meeting. For example, if you head to the middle at the start of a meeting, and see green head to the office and a few seconds later, you see them come from the caf, do an emergency meeting as the imposter won't know that you are tracking them and won't think they need to kill you. This is a huge argument and it is extremely believable because your fellow crewmates will be in awe of how smart you are when they see that you caught the imposter in the act. However, I understand that some may not be able to do this with lag or low vision, or bad memory. Try to do this when there are fewer people and there are not so many people to keep track of.
Another advantage I find is that when you stand there, you are pretty safe from being killed and as long as you stay there consistently, you won't really be blamed as several people will pass you and vouch for you just because you stood in place. Just be cautious of sabotages because people may ask why you aren't doing the sabotage so it's really up to you if you want to fix it.
Lastly, generally, I like to keep track of where everyone is, and if the imposters are big-brained, but you bigger brained, keep track of where everyone is. If you see two people run to the left after a meeting, and a couple of seconds later, someone heads into that direction, you know it's very likely them, and they should be a suspect.
Anyways thank you for coming to my TED-talk on how to catch people vent in Mira HQ and why you should stand in the middle.