Ship Building Tips

First off, I'll focus on vanilla ship building and my best practices will probably differ from others' since it will be rooted in my preferences to have a practical ship for grinding and exploration. I also love boarding ships, so I optimize for docker-to-cockpit flows.

Saving and Building

Unfortunately, there are two things to consider:

You cannot exit Ship Builder if there are any errors with your ship.
Your autosaves don't run while in Ship Builder.

There have been many times where I spend an hour working on the perfect ship only to lose it with a game crash or the ship builder save corrupts the ship itself. The latter can be especially frustrated because you're able to still save your game but the ship is simply gone from your inventory. In my experience, the chances of this happening increase with the more ships you have in your inventory. This can also happen with or without mods.

To counteract this, you might plan out your build in stages so you can continually meet minimum requirements to exit ship builder, save, then go back in and do more changes.

Basic Requirements to Bypass Errors

There are common errors and how to avoid them:

At minimum, a ship must have 1 cockpit, 1 docker, 1 engine, 1 landing gear, 1 landing bay, and 1 reactor.
Both the bay and docker must be at the outermost edges of your design
At maximum, you're only allowed 3 different types of weapons, and they must all be assigned to a button/key (eg: RT/LT/Y on Xbox).
Max power usage for engines and weapons is always 12. That means if an engine takes 3 power, you can only use 4 of them. Or if a weapon uses 2 power, you can have 6 of them on your ship.
There must be a path between cockpit, docker, and landing bay. Make sure all habs are connected to these and each other.
A shield is optional, but there can only be 1 on a ship.
More mass means more landing gears, and they must all be on the same level as your landing bay (when you highlight them, make sure the bay and all gears are showing a green surface).
All parts must be attached. A trick to find those unattached parts is to hover over a piece and press the buttonf or Select All then drags all selected pieces elsewhere on the builder. The unattached part(s) will be revealed when they stay where they're at.

Like Building a House

Multilevel ships can be fun, but traversing multiple decks in a ship can quickly become a pain. The ladder animation is neat but very slow. I usually boost pack my way between decks. Stairs don't exist in vanilla ships, so I tend to build as few decks as possible on my ships. This usually leads to:

A main deck that the cockpit lives on, and I favor cockpits that have a door opening vs. a ladder entry. Must haves for me on this deck is usually a bad (captain's quarters preferable), a workshop and maybe a science lab.
A secondary deck usually for dockers. The slim docker from Deimos is the best tool if you want to give lots of options for styling the top of your ship. Just flip that slim docker upside down and attach it to a hab below your main deck.

More Power, Scotty

In vanilla ships, it's all about the reactor and getting the most power bars you can. More powerful weapons and shields are also locked behind higher class reactors, and higher class reactors are locked behind higher levels of the Pilot skill. Your best bet, without any mods, is to grind the Vanguard ship simulator to level the Pilot skill with more ship kills. If you have mods, another great option is to grab the Dark Universe: Crossfire mod that creates extra ship encounters in star systems once you jump into one. I tend to do Crossfire in Sol (a level 1 system with lots of planets to travel to) for new characters.

Best Vanilla Ships

I'd recommend gradually upgrading the Frontier's weapons until you can afford something better.

The Narwhal (from Taiyo in Neon) is the most powerful one when it comes to the reactor, especially. It is also the most expensive for that reason, but getting it helps you skip needing to level Starship Design a lot to unlock it the reactor. The Shieldbreaker is a decent mid-tier option with a B-class reactor available at New Atlantis.

My personal favorite for look is the Dragonfire. Its mobility stinks, though, so you'll need to upgrade its engines, and it comes with a pretty weak reactor that needs an upgrade.

Landing Bays

I tend to prefer bays that have a ladder entryway (Hopetech and Deimos bays) so I can put the main deck above it. This gives the look of multiple decks from the exterior but then you can stick extra fuel tanks, reactor, and/or grav drive around your landing gear on the same deck as the landing bay.

I also highly recommend positioning your landing bay toward the front of your ship. So many landing pads in the game will land your ship facing the city/settlement you're visiting. Unless you always want to run around your ship, stick the bay toward the front.

Layouts

Without the mod, Place Doors Yourself (PDY), you'll be at the mercy of the game's decision-making with door placement. This can become a mess if you have multiple habs sitting next to each other.

Multiple decks will cause your habs to become riddled with ladders that will get in the way. Worse yet, 3+ decks will create a very tall ladder that is difficult to boost pack through even with the best packs. I avoid it whenever I can, but if you want that then try to keep 3 habs from stacking in the same spot.
If you don't want a long cooridor of habs, use fuel tanks or cargo to wrap your habs around and plan the path you'd like to traverse - especially between the docker and landing bay and cockpit.

What other tips can you think of that should be added? Please feel free to reply with any you can think of for better ship building experiences.