This can be a super tricky thing to do. I am by no means an expert, and I do think it largely depends on the personality of the person and what conversations would be considered the norm. I also think it can be more tricky if you’ve been sleeping with that person for a long time as it sometimes feels like there’s more to “lose”.
If I am trying to introduce a new kink/fantasy/idea with someone I’m sleeping with, then my go-to is usually saying… “I was listening to a podcast and they were discussing XXX, what are your thoughts on that?”. You can tend to gauge where someone is at by their response - as long as it is not a absolute no/disgust, then I will follow it up with questions or comments like, “I find it quite hot. I think that’s something I’d like to try - would you be up for it?”. Just as an example! I think the more casual the conversation the less awkward it’s going to be. I’d much rather have a chat about a podcast/article I’d read than a formal sit down “we need to discuss gags”.
I also find sexting quite an opener and people tend to be more open about what their fantasies/kinks may be. Understand this is much harder if you already live with them! Even if you follow it up at a later date… “You know when you mentioned XXX the other day when we were texting, is that something you’d like to explore?”
Another way I’ve heard people do before is to both write all their fantasies down or things they’d like to try. Then to compare lists, say what you’d like, what you’re unsure of but you’ll give a go, and what your limits are/hard no’s. This would obviously need a trusted space and a precursor for no judgement!
I like to think now that anyone I’m sleeping with is likely to be open to at least a conversation about things, even if they decide they don’t want to do it (which is absolutely fine). It’s overcoming the insecurities in myself, and like @Mint-Monster said, overcoming the message that “woman aren’t meant to enjoy sex” that we’ve been brought up with.
I also think it’s super important to acknowledge that not everyone will enjoy the same things and that is absolutely okay. We shouldn’t be shamed for liking something, and shouldn’t shame people for not liking things. Just like food… We all have our favourites and absolute no go’s!