Advice for ship designing...
Well firstly, I always intend to design ships as part of a set, so I try to make sure there are common elements found in every design throughout the set usually.
1) I always start by designing the Medium class ship, this is the workhorse of many navies and so it comes up a lot in games, this will then guide me for the Large, Huge, classes.
2) Once I've designed the Medium, I'll take note of what engine designs I used, as well as any weapon platforms, command modules, etc. and make those into custom components for reuse often.
3) The other thing I do, is I try to establish a guiding style before I continue, this usually comes down to: Organic, Classic, Retro, and then Vertical or Horizontal.
Ultimately, I don't often try to replicate ships from other source materials so I'm usually just playing with parts and trying to make something that looks sensible. I'll also be careful with colors and parts, some parts just look mismatched together no matter what, and that just doesn't get allowed. I'm not saying I don't have inspirations from other sources, but I'm looking to be original.
Usually the Medium, Cargo, and Tiny (Fighter) hulls take me 2 hours each, and then subsequent ships might only be a hour, but of course, sometimes you just have problems and it takes longer, I always construct all designs multiple times to see them in game, and I try extremely hard to avoid any clipping whatsoever. Variant classes with modifications are also usually only a hour or so. To date, I've played 290 hours of the game. I'd say 200 of those are ship designing, probably about 50 is testing and learning and 150 is straight design. I think I've produced about 100 designs to date.