The easiest 3D software to get to grips with is Google Sketchup (in my opinion).
It is very intuitive and completely free, and you really can model just about anything.
Lots of tutorials about too, regardless of what software you use.
Over the summer I've been using SolidWorks, and that's great - there is a similar piece of software known as Creo - and with a little thought can be used in much the same way. Creo is also free if you are a student
Like ollite says, take things slowly, and work out how to make shapes. The usual method is to work in one view at a time, (top, front, side) to make the shape look right from each angle, then the 3D shape appears by itself
Good luck
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