Creating small details
Next, let's make some small parts. These things will be duplicated and placed all over the ship, so it's easier to just model one of each and then move them into position. The more copies of each one that you plan to make, the lower you should keep the polygon count:
Before duplicating, of course, we'll want to add our materials:
Here's where I ended up putting the RCS/OMS thrusters (on 1/2 the ship):
The thrusters can be any size (scale) that they need to be, but the handles and lights are a little different. These should be related to the size of a human. To make sure we get this right before making a lot of copies, we can just add a quick human model to our scene (or at the very least, just a cube that's as tall as a person would be):
This will give you a good sense of scale and allow you to get your little details right. For instance, it wouldn't make sense if the EVA handles were larger than a human. Nor would it make sense if the running lights were larger...