The guidelines are, in many ways, for new writers, or for new writers who hope to treat the Worldcon as an entry into the professional world. They're very helpful, excellent pieces of advice, to which I would like to add:
2a. You can learn a lot by attending program items featuring agents.
At Confluence, someone asked me how I had gotten started (to which I replied, submitted my first novel to Del Rey), and how I had found an agent (to which I replied, I approached one in person, spoke to him about the Lester Del Rey response said submission had initially received (which was a "not this book because x, y, z, you moron, but if you fixed x, y, z, -then- you might have something worth reading", and no, it wasn't really a figurative moron <wry g>) and asked said agent if he had any interest in reading the revision.
The young man replied, "You talked to an agent?? But how? No one even showed any interest in my query letters."
And I answered "I went to a Worldcon, went to all the panels that agents were on, listened to all of them talk, and then approached one whose name I recognized from prior research and who I thought had spoken well."
This hadn't occurred to the writer, but I sort of assume that's a large part of the reason agents take on a public role on panels at Worldcons (my current agent, afaik, has never done a panel at a Worldcon since I started going to them).
sartorias's rule about not taking a 500 page manuscript (or larger, so no rules weaselling) to hand to editors also applies to agents. No one is going to read it at the convention, so unless you've made prior arrangements to deliver it there, don't.
I'd also add one last rule:
5. Have fun.
I'm dead serious about this. An interesting and relevant aside: Another author of my acquaintance asked me just this year about an editor we had both met at a convention (local). I said I didn't know much about said editor, but that yes, his general persona implied a certain distance or testiness, and then asked why she thought I'd know, since I don't publish with his house and have never worked with him.
She said, "You always seem so plugged-in."
You could have knocked me over with a feather. I pointed out that she went to far more conventions than I did; with the children at home, I go to one or two a year (okay, one a year until the last two years). Her turn to be surprised, but she went on to observe that I must be good at networking.
Okay, that feather thing again.
Once I got up, I thought about what she said. I think it comes down to this: I don't do anything that doesn't look like fun. This goes for everything at a Worldcon, including talking to editors. If it's not fun to speak with a specific editor? I don't do it. I am guaranteed to get away from home once a year, and even if it's in theory for business reasons I'm selfish enough not to want to spend that time putting on a fake smile and pretending I'm enjoying something I'm not. If it's fun to speak with an editor, even if I think there's no chance I'd ever submit to them (or that they'd ask <wry g>), I speak with the editor. Ditto pretty much everything else at a convention.
Because if you're there to "network" and you're having a miserable time? I don't think it does you any good at all. Unless you're a fabulous actor, or at least a much, much better actor than I am <wry g>. For the last several years, I've had no conscious awareness of networking at all. But I guess, from the outside, it looks like I must.
Plus... networking is part serendipity, and sometimes it's decided far after the fact. A number of the people I met and liked in, say, 1989, were not "anybodies" of note at that time. Many had just begun, like I had, to dip their toe into the publishing pond. I enjoyed talking with them because it was fun, and as they wore no editor/agent/famous author badges, that was, in fact, the only reason to do so.
But... Years later, some of these people were editing, or selling a lot of novels, etc., etc. Seeing them now is still fun -- but it looks like networking from the outside because the history isn't as obvious.
5a. Go meet your peers.
People who are in the position you're in now will often be in the position you're in later, and they can make soldiering in the trenches, if not fun, then a lot less isolated.
Some of them, though, will begin to edit anthologies, some will have done well enough that they might offer to read and cover quote you, etc. You won't have any idea right now who those people will be -- but if you really feel that you must justify every moment spent at your first Worldcon as a business moment to justify the expense of being there, think of every unknown as a future possibility <g>.