2) What time are guild missions and where do we meet up? - Guild missions occur on two days: Sunday (main) at 3pm CST (9pm UST server time) and Thursday (makeups) at 9pm CST (3am UST server time). We usually gather in the guild hall beforehand. We will let you know in guild chat where we are meeting and going next. Reminders for guild missions typically start approximately 1 hour prior to the start. See http://gw2myth.enjin.com/forum/m/16306359/viewthread/11422692-guild-mission-locations-map for details and frequent guild mission locations.
3) What is server time? - Server time refers to the time zone that Guild Wars 2 runs events off of. Server time is the same regardless of what server you are on. Server time is based off of Coordinated Universal Time (UTC).
4) How do I know what the server time is? - A quick way to check is to press "H" and go to the achievements section. Under the Dailies, it will show a timer countdown to reset. You can set your in-game clock to server time under Options, In-Game Clock. Then the clock in the lower left hand corner of your min-map will display server time.