As FSMan says, start out nice and simple - learn the basic tools first and then move on to making more complex objects and scenes. Try some of the freebies on this site first to get a feel for things (these are in a suggested order too):
http://www.simplylightwave.com/movie...mhtml?tut_id=8
http://www.simplylightwave.com/movie...mhtml?tut_id=9
http://www.simplylightwave.com/movie...mhtml?tut_id=4 (Parts of this will cost points - only the modelling part is free)
http://www.simplylightwave.com/movie...mhtml?tut_id=3
http://www.simplylightwave.com/movie...tml?tut_id=506 (Again, only the first part of this tute is free)