This may sound a little stupid and insulting but, this is the advise somoen gave me once. Start small somthing easy but impressive, I made a SS dagger, nothing special but was made out of MDF painted and then drypainted to give the illusion of wear and tare, since sold it so no pics sorry, but dry paintings a good technigue to have under your belt, as seen on the river Song blaster in post #4 also fantasy guns are good as you can go to any £1 store in the UK and buy a cheap blaster of some sort that you can modify, I also buy Aircraft & ship model kits as they havesome great bits and pieces to add to your basters, guns, and even daggers, knifes and swords, as well as anything else you can dream up from the movies, aferall if its good enough for the Death Star its good enough for me - lol
There are loads of tutorials on youtude and the guys in this forum are without a doubt great at helping out, just remember it does not have to a fullsize replica of the Death Star to start with try a Lightsaber, they good, I made one from some plumbing supplies my mate had in his garage, not a great model but then It was made by a Padawan (Me) looks good from a distance and holds up to the kids bashing it pretty well, so give it a go, whatever your thinking of making make sure you have all the matterials and tools ready as its not much fun trying to find a shop open on a sunday afternoon that sells Bondo or some sort of modeling clay.
Good luck and most of all have fun makeing whatever your going to make, afterall thats the reason we do it ....