Jay answers: Congratulations on your new relationship!
There are a number of important or key topics that people entering into a new relationship probably feel they should disclose. Similarly there are questions they probably want to ask. Assuming you see long-term potential in a relationship you probably want to know all sorts of things about the other person. Are they close with their parents, how do they feel about children, how many pets do they have/want, are they deathly allergic to your favourite food, where do they want to live later in life?
Learning whether your partner has any naughty fantasies or kinks is certainly a good plan if you want to build a future with your partner. The other side of that coin is you should let them know about any special sexy desires or practises that make your heart skip a beat. I hope everyone agrees this is important information to disclose, but the tricky part of the situation is: when do you share this information? On the first date might be too soon, but you should definitely tell them before the wedding night.
I'm in favour of sharing information relating to your sexuality sooner rather than later. Whether you're telling your new significant other about a hot fantasy, a kink, your orientation, or STI status I think it's better to share too soon rather than too late. Maybe not on the first couple of dates, but probably shortly after that.
While I do advocate for early disclosure, I don't think you necessarily need to share everything in your Top Secret file all at once. If you want to peg your new boyfriend, maybe just start with a conversation about how he'd feel about a little booty play. If he gives you a hard "no" to a finger in or around his bottom then chances are there is no point in throwing pegging into the conversation. Likewise if he's tuned off by the thought of using handcuffs, you can probably skip telling him about your fancy rope collection.
On the other hand if you get the green light in early conversations about the introductory level versions of your fantasies, then it'll pave the way to have additional conversations in the future and you can gradually ramp up. I talked about some approaches you might want to take when sharing kinky fantasies in a previous post.
Something else you may wish to consider is making sure when you share your fantasies with your new partner that you let them know you don't necessarily want to engage in these activities right now. I find conversations about fantasies are usualy best done when clothed, sober, and with the lights on. I also like to make sure my partner realizes when I bring up a new fantasy or kink that I don't mean we should dive into it right away. There is a big difference between saying, "I want to tie you up and take turns banging you with my best friend" while holding a coil of rope versus saying, "You know what would be fun sometime? Mixing some bondage into our sex life."
In other words, give your partner time to process what you are telling them without any sense of urgency. They shouldn't feel like they need to make a choice right away or that you want to rush out and engage in your fantasy this instant.
Basically, my advice is to start easing your new partner into the idea of your fantasies early, but in small doses, and without any pressure to respond or participate right away. For instance, if group sex appeals to you then you could check their temperature about threesomes and ask them about how they feel about the idea of trying sex with a guest star while at dinner one evening. This will go over smoother than asking him to film your orgy on the way to the hotel.