Well I don't use Truespace, but the principals are the same in any 3D modelling program. It depends on:
A.what the models are for
B.how confident you are with 3D
If you just want to make renders then I suggest that you use modified primitives for the simpler components like Cannons etc. And spline objects for the more complex parts like the main hull and wings. If you're not sure on how to use splines then there are lots of tutorials available. Also when making a ship, it's best to make the biggest features first, this gives you a good base to work on, and usually avoids any problems with things being the wrong scale. There are lots of different approaches to it, basically you have to find the one that works best for you.
If you are new to 3D then it's probably best if you start off by getting some practice in using the different tools first, then go and make a ship.