The trial starts up this coming Thursday and runs through Sunday. As long as you don't have a current Star Wars: The Old Republic account (and haven't had one prior) you can take part in the festivities.
Individuals who take part in the Weekend Pass will be able to experience the opening adventures of each of the eight character classes in the game, exploring both their Origin World and may even have the opportunity to visit their faction’s Capital World. Additionally, Weekend Pass players will have the chance to face off against other players in PvP Warzones, or join up with friends and play through a couple of early faction-specific Flashpoints in the game, The Esseles and The Black Talon.Sounds like a good, solid, amount of play time right there. For anyone who's on the fence about signing up for the 'full game', you might want to clear your weekend gaming schedule because this should make up your mind for you.
The trial officially starts this Thursday the 15th (you can create and register your account then too) at 12:01 CDT and ends on March 19th at 2:00am CDT... which seems like kind of a strange time, but whatever floats the boat.
Get the full skinny right here.