Comments
Kit's answer was very good and I agree with all of it, especially "make sure they have something to remember you by". A physical thing they can put in their pocket, like a business-card-sized-thing or a small/foldable pamphlet, seems good to have available.
I'd recommend editing your answer to make your relationship with the conference more clear. Are you involved in venture capital or some other branch of finance? If so, it's probably good to start off with that in conversations, rather than leading on the fact that you want to talk about charity. If you want a fun venture fact for these conversations, you could mention that 80,000 Hours and CEA both went through Y Combinator and/or talk about the rapid growth of Founders' Pledge.
Don't be afraid to let people go if they don't seem interested. The card/pamphlet idea I mentioned above is good for this -- allows a conversation to break up "politely" as they take something and you leave -- or you can think of a good "script" for what to say when you don't think the other person is engaged. You won't have time to talk to everyone even if you move fast (I assume), so there's no loss in cycling through people quickly until you hit someone who "gets it" and wants to hear more.
Immediate, not hugely informed thoughts: (I've talked to ~250 finance people about EA but only attended one finance conference, and it was fintech rather than investment.)
Broadly I'd recommend looking at generic sales advice, including some conference-specific stuff. A big thing is making clear quickly why you're relevant to someone. What can you offer them? Why will they care? What is the one point you want them to remember? They'll have little time, probably being very focused on finding potential business partners, e.g. funds looking for investors, if this is the kind of investor conference I'm thinking of. You might have to be even more prepared to demonstrate relevance than others at the conference because you are not obviously part of the main theme or expected to be there.
Also, how familiar are you with how these kinds of people think? Can you frame EA in industry terms, for example? Seeking to maximise (social) return on investment seems uncontroversial and used as a concept in impact investing. I've also tried talking directly about comparing charities (comparables, alpha) though that seemed to not translate as well. (Anecdotal.)
The handbook here may also be of tangential relevance: http://eaworkplaceactivism.org
Another tip is to expect an extremely low hit rate. Figure out who seems interested in thinking about their giving and focus on them. Think about whether you want to follow up with the most promising people to point them to key resources or connect them to other interested people. Figure out if asking for contact details is normal or weird in this context.
Good luck. There don't seem to be major downsides, so even with a low hit rate, seems worth a shot.
Thanks very much! And the workplace activism handbook looks interesting even though it's not directly related to this particular project, so thanks for that too.