The multi-player Star Wars, World of Warcraft clone will be having a free weekend, the page for which is here. The first free weekend is “Thursday, March 15 at 12:01 AM CT through Monday, March 19 at 2:00 AM CT.” There are some more details here.
The trial will have certain limits such as chat being blocked and restrictions on “Origin World, Capital World, the Fleet, all Warzones, and in their first Flashpoint”, and a level cap of 15.
It should give you a good idea of what the game is like and likely get you hooked in. My advice is to skip it and just play Star Wars: Knights of the Old Republic which costs the same as a one month subscription to the newer MMO version. It’s even better if you havent played the single player game before but if you have just wait for Guild Wars 2 or something.