Being the guest star
Let's start off with the sort of things you can do when you find yourself a rather infrequent attendee to the roleplaying circus. Change starts from within, after all.
The first thing you need to do is have an explanation for why your character will suddenly vanish every now and again, sometimes for extended periods. It doesn't have to be a wild and ornate explanation, but there does have to be some reason given. Maybe your character travels a lot, maybe she's prone to flights of fancy that take her outside of the regular social circle, maybe she works for the government and doesn't always know where she'll be from week to week. Heck, in some games she could plausibly be a criminal who gets caught on a lot of minor charges. The point is, when she's out of action for a while, you need a reason, and it needs to be something both consistent and low-key.
Second of all, you need contacts. If you want to jump in and enjoy the time you have with others, you need to get brought up to speed quickly, and knowing one or two social butterflies can help that process immensely. These are the characters whose players should likely know that you'll be here and there for a while so that they can expect to give your character a rundown whenever she crops up again. Consider it a basic courtesy.
Those are probably the easy parts. The next part is far more difficult: letting your character fill the role of a guest star instead of a main character.
My choice of terminology here isn't entirely arbitrary. Guest stars in a regular series show up and are interesting; maybe they even have an episode or two of their own, but they aren't the central focus of the show. It's generally implied -- if not outright stated -- that the character has a social circle and a set of obligations not directly connected to the stories of everyone else on the show. And if your character is going to be around intermittently, you have to let her occupy that role, making her someone interesting but not really the center of attention.
This is something that most roleplayers aren't really great at. We create characters; we want them to take center stage. Most people are able to learn about sharing that stage, but all of us want our characters to get a moment or two in the sun. But if you can't be around on a regular basis, you need to let your friends continue roleplaying without you around, and part of that means not shackling major character developments to someone with an irregular presence in the game.
Romance? Probably out, aside from occasional flirting. Deeply interwoven backstories? Workable, but you'll have to make sure you can keep up with developing changes. Rivalry? Not really going to work out when you aren't around very often. You can still have a notable impact, but it's going to be one defined in part by your absence rather than your constant presence.
Last but not least, whenever possible, let people know either where you are or what you're going to be doing so that your sudden disappearances aren't a mystery. (Personally, I'm just up-front about what I do for a living. That explains a lot.) Very few groups will fail to understand someone whose presence is irregular based on outside circumstances, but no one likes dealing with a player who just randomly vanishes and then shows up again without explanation. One smells like the sort of real-life stuff that gets in the way of everyone; the other smells like laziness. If you don't call for seven weeks for no reason, we're not dating any longer.
Dealing with guest stars
So you have a recurring guest star, and for the purposes of discussion we're going to assume this person is a decent roleplayer whom you actually want around. (Otherwise, your plans for dealing with the absent player are some variant on "change servers without telling him.") How do you deal with the guy who's only around every so often?
First of all, whenever possible, try to have some story arcs and character elements that center around the guest star, and bring those out when he's around. That's not to say you should put all other roleplaying on hold when the guest star is in town, but if you can try to focus a little more on relationships between the infrequent character and your own, it'll make both of you feel more invested -- he because he's getting attention; you because you're getting to bring in character elements that you don't always get to explore.
Having regular events, such as a weekly meeting of some sort, can help keep the guest star involved. Sure, he might have been out of the game for a month, but at least he knows when all of the regular stuff is happening. Try to plan events with the understanding that if he's playing that much less, his character is probably not in the same gameplay band as people who play on a regular basis. I know that I espouse having events that aren't just a bunch of people standing around in a room, but your frequently absent player might be best served by just such a gathering.
If you can, try to keep going regular forum posts that update any and all members-in-absentia on what's been going on while they've been away. This can be helpful for regular players as well -- it can be a lot to keep up with everyone's individual actions at times -- but it's most useful for players who might not be present for every minor event. Some players will even happily make up the difference with forum roleplaying, depending on the reasons keeping them away from the regular game.
Last but not least, especially if you're a guild leader, try to have an open means of communication with your errant roleplayers. If there is an actual problem with the long absences, you want to have some way of letting the person in question know, and it helps to have an idea when the player is coming back. For some players, this can dig at the sense of verisimilitude just a little, but sometimes you need to take a hit to immersion to keep communication active. And you know what a fan I am of communication.
That's it for this week's column -- and as always, I welcome feedback to firstname.lastname@example.org or via the comments below. Next week, let's try that breadth of roleplaying thing again, hmm?
Every Friday, Eliot Lefebvre fills a column up with excellent advice on investing money, writing award-winning novels, and being elected to public office. Then he removes all of that, and you're left with Storyboard, which focuses on roleplaying in MMOs. It won't help you get elected, but it will help you pretend you did.