Taken from Wikipedia, the most reliable source in the internet, never failed and never lied, all hail to thy hypno toad:

Casey Hudson, Project Director for BioWare, has said that players should keep their Mass Effect save-files,[2] because decisions made by the player in the first game will continue to have influences on their character in the sequel.[3] Players who have not played the first Mass Effect will start a new character in Mass Effect 2, and will be brought up to speed on the story elements that have taken place thus far in the series.[4] It is highly recommended, however, that people play the first game before playing the sequel. Hudson also states that characters from the previous game will come back, provided that they were not killed. The first trailer for this game indicates that Commander Shepard has been killed in action. It is uncertain whether or not this is the case given that players have been asked to keep their saved game from Mass Effect as well as statements from developers in the past which have implied that Commander Shepard will be the main character in the planned Mass Effect trilogy.