The following were compiled by myself and David Holtzman, and while it is far from comprehensive, we hope that it will help those looking to excel in Guild Wars pvp.
1. Using "me" in voice communication is counterproductive. Use your number (preferably, since it's faster to select someone by number) or your character name. This is probably one of the most often-made mistakes when using resources such as Ventrilo/Teamspeak.
2. Versus spikes, advance warning is your friend. If the spike includes one or more warriors, call if they focus on you. You're probably about to be spiked. The same applies if you are suddenly drained of an enchantment, Shocked, or otherwise picked out.
3. If you are doing something that could put you in potentially above-average danger (warrior using Frenzy in a high-damage environment, running a relic, body blocking, running into a trapped up area et cetera), your monks will want to know about it. If you want to survive, you will want your monks to know about it. So let them know.
4. Though it's best if everyone can communicate clearly, this does not mean everyone should be leading. Eight people all saying what to do leads to a complete lack of coordination that gets you killed. While having a "caller" is most apparent in dedicated spike-type builds, having someone designated to direct the overall tactics of your team will produce better results.
5. If you do have a strat caller, do what they say! It is very unlikely that going off and doing your own thing is going to work out better than acting together.
6. In addition to having clearly called strategy during the match, preplanning is your friend. On maps where you can see the other team, take advantage of this and make sure the team has an idea of roughly what is planned for the upcoming battle. If circumstances change, plans can change, but having something to start out with saves a lot of confusion during the initial stages of the fight.
7. If you are unable to perform some form of character's function (skill diverted, edenied, interrupted, or the like), let your team know. Don't sit there hopeless and then complain about your inability to function after the battle. If it's critical that you be able to function, the strat caller may need to orient the focus of the team towards the source of shutdown, but they can't if they don't know about it.
8. Interrupts are a terrible thing to waste, especially when it's on a capping Ghostly Hero. Don't blindly spam them, call ahead of time when you plan to interrupt. If you call an interrupt and it fails, let your team know so someone else can take it. Two to three interrupts properly chained are just as effective (if not better) than a larger number with no coordination. Even better, plan ahead of time the order of interrupts.
9. If you're interrupting, make sure everyone else always knows which enemy you're on. If you're ally-assisting, make sure everyone knows always which team mate you're helping.
10. Not every fight goes well, but losing your calm will only make it worse. Screaming at people on vent doesn't make them save the day, but does distract them from a battle that's already going poorly.
11. If you notice an apparent flaw in the current strategy, but aren't calling strats, don't start competing with the strat caller - instead, inform them of your observation. There may be other factors being taken into account with the current team strategy that are not immediately apparent. Though certain things are time critical, many others are of less importance than maintaining a cohesive team.
12. Calling for efficient hex and condition removal: Don't call for condition or hex removal if you don't need it. The only reason for removal is when it hinders your job. So don't call for removal on a blind elementalist or a dazed warrior. DO however, call important hexes - things like Migraines, Spitefuls, et cetera. In addition, don’t call for useless removals – e.g. if you’re standing in a dust trap, don’t ask for a condition removal until either it finishes pulsing or you move out of it.
13. When monking, don't call what sort of hex removal you're using (exception of Convert), just call "Hex #". The other exception to this is if you are pre-veiling someone (if they are being spammed with Diversion, or such).
14. When playing warrior, make sure any other warriors are always aware of your adrenal status.
15. When you use an area based skill, always let your team know where it is. If you see an area based skill that isn't yours, make sure to call what and where it is.
Feedback, additions, and comments are always welcome.