Greetings!
I often find myself with a not so experienced crew, and there's a pattern to their question, if they care to ask and be helped. Supposedly most of you get the same feeling, and I'd like to collect those questions and the answers to them in a guide here. I'll fill in what I remember just now, and add to the list whenever I stumble upon something new, or another player suggests a addition (that's you! Yes, you!). Feel free to correct and comment my work, I hope we'll be able to gather many more questions and answers!
What is more important to repair? Balloon or hull?
Basically the hull is the most important component - if it's destroyed, your ship's gone as well, and the enemy scores one point. Just after it comes the balloon, because once the balloon is down your ship will start sinking until it crashes into the ground - which in turn damages the hull until the balloon is repaired again. If your captain doesn't tell you otherwise, you can usually try to keep those two up and then tend to engines and guns. However, your captain might want to keep the balloon destroyed for sinking faster for a moment, but in that event he'll tell you anyways. Also, if you're running away from a enemy ship it might be more important to repair the engines than the guns. Use your best judgement if your captain doesn't give you instructions on what to repair first, but always keep an eye on hull and balloon.
What's the best gun?
A heavy flak is less effective in close quarters and a gatling won't do much if you aim for the enemies balloon with it. There is no best gun, there are just situations where one kind of gun is more effective than another. In short, you can distinguish them by the component they are most effective against:
Good against balloons(Flechette Damage)
Hellhound Heavy Twin Carronade
Barking Dog Light Carronade
Lumberjack Heavy Mortar
Good against the hull's armor(Piercing damage, against the part of the hull that can be repaired)
Whirlwind Light Gatling Gun
Mercury Field Gun - Can also be used to take out certain components effectively.
Good against the hull's health (explosive damage, against the part of the hull that can't be repaired)
Typhoon Heavy Flak
Echidna Light Flak
Scylla Double Barrel Mortar
Good against components(Shatter damage, components are guns and engines)
Manticore Heavy Hwacha
Banshee Light Rocket Carousel
Artemis Light Rocket Launcher
Special cases
Dragon Tongue Light Flamethrower - Fire deals more damage against the balloon, but more importantly, it makes all the components on the other ship less effective and can even destroy them or render them unusable.
Beacon Light Flare Gun - Shoots a green flare that lights up the area where it goes down. Excellent for seeing enemy ships in a cloud.
Javelin Harpoon Gun - Pulls you and the enemy ship together if it hits, good for ramming and probably confusing the enemy captain.
What happens when I fall off the Ship?
Nothing, really. You just get teleported back to the middle of the ship, but lose valuable time in the process.
Are there any benefits from leveling up or getting achievements?
You just get some cosmetical stuff with every couple of ranks. You don't unlock any other ships, guns or tools.
(Modified the light mortar location. Is it terrible for balloons, lol. Zill)