1 - Get psyched. I'm an introvert and this is going to be hard. It is work and as such it may well be fun, but it doesn't have to be. I did not come here to do easy things. Let's rock!
(the other half of that, of course, is "be ready" - save energy for the event, and schedule recovery time afterwards. Make a conscious decision about whether the opportunities are worth the power consumption)
2 - Full tank. I've done whole evenings where I never quite made it to the bar, always running into someone else I knew, or wanted to speak with, or wanted to speak with me, on the way. So don't arrive hungry, or thirsty. You're paying too much for this to eat free food.
3 - Look far ahead. I'm not there for clients. I'm not even there for immediate joint ventures. I'm there to increase some overall Connectedness Quotient that, over the long term, through an unclear mechanism, seems to provide needed connections at appropriate times.
4 - Trust your gut. Some of my best connections have come from a feeling of "I know you're going to be important at some point; I just don't know how yet".
5 - Paper is temporary, but useful. Every neuron that's spinning on short-term storage ("that guy, what was his name?" "who's the VIP I need to meet at some point tonight?") is not available to fully connect with whoever's speaking to me, and I owe them that. So: as often as possible, brain-dump to a notebook and forget. Using a notebook (visibly, though while not talking to anyone) doesn't seem to be weird. I could use a phone but I find that actually more socially isolating.
6 - Pivot. By far the easiest way to make the initial connection is to know person A. When they're speaking to person B, wander up, get introduced. C, who knows B, will join at some point. A will drop out of the conversation later on, but by then you have two more pivot points. With half a dozen pivots you can meet everyone in a room. Work this process consciously, and work to assist others who are using it (even to the point of 'if you spot D nearby who you know, flag them down and pull them into the group').
(The corollary being that if you have zero initial pivots, you're in trouble and are going to have to do this the hard way)
7 - Speak (in public). There's no real point in going to conferences unless you're presenting. For other events, look for ways to get involved in speaking/production - it's an instant icebreaker with everyone else there at once. Use this the other way as well - remember talking points from speakers' sessions and use this to start a discussion with them.
8 - Don't speak (in private). I'm there to listen to people. I don't want to talk about me, beyond the minimum necessary to maintain the connection. Most incoming questions can be answered (though not at length), then conveniently reflected. What I really want to do is find out what they're excited about or working on or troubled by right now, and then talk about that - solving problems together is fun and useful.
9 - Names names names. Spaced repetition from the notebook helps here. Also that silly visualisation thing ("Hi, I'm Denise" [momentarily notice their knees]) really does work. It sucks but use it anyway.
10 - Victory lap. I usually leave suddenly at 80% of [time, energy, opportunities] used. My practice is generally to make eye contact and wave at the key people, without pulling them out of their conversations to say goodbye. I don't know if that's better.
11 - Brain dump. Paper is temporary, unsearchable, useless in the long term. Don't hoard. Reprocess notes the next morning, discarding half of what was written down, and loading the rest, in abbreviated form, into Ally or nvAlt. Then throw the paper away.
12 - Followup. I don't tend to do this automatically, because it feels too mechanical, like making an excuse to speak. But it's worth adding everyone's blogs / twitter / podcasts/etc to my normal feed, glancing at the top item, and starting a conversation on it if it's relevant.