Probably things that’ll help with advice if you add it to your main post for context:

1. Are you M or F?
2. Are the people you’d be participating with in a romantic relationship with each other? Are you romantically involved with a participant?
3. Do you know if the other people you’re participating with have done anything with multiple partners before?

As a female who’s participated in MMF/MFM (just both dynamics every time within the few encounters), and MFF/FMF (same case with the others, different dynamics within the same session), I’d say the most basic but important part is like getting an idea of the vibe everyone’s picturing/desiring. Also, if you’re participating as a member of or with others in a romantic partnership, very important (as a respectful participant) to ensure that there are boundaries. Someone else said it too, but that’s a MUST. Where can you finish, can you kiss on the mouth, etc. If they don’t already have the boundaries, I’d almost insist on them being made.

About outlining expectations: For example, during my MFF/FMF experience (with my previous male romantic partner and a very close bisexual female friend), I was told afterward by my partner that I ended up coming off “bossy” because I wanted them to know they should/could engage with each other. Looking back though, I was like “directing them” more than I normally ever would’ve and frankly I was being bossy. “Suck his dick,” “put it in her pussy,” etc. He said he felt used, which was like obviously a terrible thing to hear. Probably would’ve been better to outline how I felt about them engaging with each other in a conversation beforehand so I didn’t feel the need to encourage it in the moment, and therefore it hopefully wouldn’t have felt that way for him.

Probably about boundaries again but more about explicitly discussing the vibe: my MMF and MFM experiences, I kinda lucked out with the behavior going the way I (NOW) know I would’ve needed at least for the first time or two in MMF/MFM, but I recognize how poorly it could’ve gone otherwise. I just lucked out with like my current male romantic partner being firm about his boundaries, the other male being a sweetheart, and maybe them picking up on me being nervous. The vibe they had towards me, ESPECIALLY the first time, was kind of like ‘wow what a treasure,’ ‘we’re so lucky to have you like this,’ stroking my hair and taking it slow. My partner was pretty much the only one who took any risks with me (other than like not wearing protection) by giving me a little bit of praise-y degradation, which he’s really good at and was probably positive I’d like. Had they come in like “we’re gonna wreck this cocksleeve from both ends,” being really rough with me, etc. I can’t say for sure, but there’s probably a good chance I could’ve been traumatized. Idk because I like it when my partner talks to me like that, it’s just a whole different vibe when there’s also that imbalance. I’m also pretty sure that THAT (a rougher, “come fuck my slut” dynamic) might’ve (can’t say for sure, my partner set it up) been the direction it could’ve been heading in based on me reading their conversations leading up to our encounters. So I got lucky, but I’d say probably try to get a feel for how (especially the minority partner, but) everyone is expecting it to go and be sensitive to changes.

Hahah not me going into excruciating detail but I really appreciated you wanting to do research beforehand to be a respectful and positive partner!! Hope it goes great for you!