make friends, not contacts
The biggest advice I can give to a budding networker: Make friends, not contacts.
I say that not because you're going to be best friends with everyone. This is a business like every other. But it sets the stage for genuineness. The minute you start selling, all your authenticity goes out the window.
It's not all about you. Only talk about your project if someone asks. Give them a conversational ONE-PART tag line ("it's an epic fantasy about this badass guy falsely accused of murder"--Exile). Their next question is unlikely to be about the story. It's more likely to be about what state it's in (it's okay to say revision, or draft or whatever, even to an editor) and maybe a little about how long you've been working on it and how much fun you're having with it. This is NOT the time to bitch about it in any way: you have no time to work, your wife hates that you write, you're stuck in the middle, your kid's homework is too overwhelming, etc. That's for private. This is public. You're networking. You're on. You're a writer who wants to sell. This is that public persona I talked about at the beginning of the series. (Of course we're all guilty of this. I am. But seriously. Don't bitch.) Anything you can say meta-cognitively about your work is okay though. Quick anecdote: I once had an editor really interested in the story of SILVER SCAR. I told him I'd love to send it to him, but it wasn't ready. He asked "Why?" That's a big question, because the book is written. I told him I wasn't confident enough yet in the world-building; it needs firming up. He was highly approving and told me insufficient world-building was one of the issues with work he turned down.
Do introduce people to each other. Again, this isn't all about you. A particular editor might not like your work but you might have a friend with a book right up their alley. If it works out, they'll both be glad you introduced them.
Ask editors and agents about their projects. (Agents are often reticent about talking about unsold projects; you can ask them what they've sold lately that they're excited about.) Plus, there really is no one more excited about a project than the editor--except for the writer--except by then it's much newer to the editor than it is the writer, so in the publishing time warp continuum, editors with a project in hand are often the most excited about it. Writers and agents have usually moved onto the next project.
Writers love to talk about their WIPs. They are much less interested in the project that's coming out soon. To their mind, the detachment process is often already well-launched. For instance, EXILE comes out in February. I'm tre excited but I don't have a ton to say about it. I'm actually spending my days working on EMISSARY. Right now that's where my heart and mind are.
That said, in my experience, the last thing a bunch of writers who get together at a con talk about is writing.
Ask fans what they're reading. DO NOT say "Oh, then you'd like my book or that sounds like my book." Ugh. People loathe being sold to. Just take it as another reader would: "That sounds fun. I'll look it up." Or you can, very gently, namedrop: "I'm so glad you liked that. I'm friends with her. I'll tell her you mentioned it, she'll be so excited!" (as any writer would be, unless they're an asshole) A reader will ask you about your stuff if you've made the right impression, which is down-to-earth. People who don't write think writers are like, somebody. Seriously, they do. To them, especially if you're published, you're a celebrity. And what's the cool thing to say if you've met Bono: "He's so down-to-earth." That means two things: Bono really is as cool as we think he is. PLUS you got to talk to him long enough to learn he's down-to-earth. So if you are, as a writer, down-to-earth and fun to talk to, a reader will ask you about your books or at least remember your name and look you up later.
You need business cards. And they need actual contact info, phone number, email, and your picture. They can be creative; you work in a creative industry. I'm against weird-sized cards though. I'm also pretty adamant about card etiquette: Don't hand them out unless asked or unless you're asking for one. Period. Handing out unsolicited cards stops conversations: they are usually exchanged at the end of conversations, plus the recipient feels obligated to look at it and make a comment. Also, no need to ask an agent or editor for a card. They will offer if they want to keep in contact. A surprising amount of them will give you a card unsolicited though.
Be thoughtful about doing people people favors. (unless it's buying them a drink--that's fine). Especially buying people things, especially when you don't know them well, comes off weird and makes people think they now owe you something. Remember, a favor is something that's often, to many people, a favor waiting to be called in. Probably a good rule of thumb is if you don't know their emaill address or phone number, don't start offering stuff.
Don't hold court. And mostly avoid people who do. I tend to gravitate away from those who do. They tend to be the sort of person who never turns off, and it's tough to have a meaningful conversation of any sort in that situation.
Lots of publishing folks are introverts. Trust me, most are relieved to have someone come talk to them if they're standing there alone. But don't be weird about it. Watch for clues it's time to back off and behave very professionally. As a short female often surrounded by men because more men than women write and edit SF and Fantasy, I can't count the times I've had inappropriate statements made to me or touching. (not everyone likes to be touched; I don't particularly unless I know you).