There is very little info about the game. This is meant to help folks just starting out.

1. Crew. You start out with one crew member in each of your stations. They are in the "Basic" slots. You also have expansion slots for each station. Buy crew members for the expansion slots, the  credit ones are fine and cheap. The basic slots are opened up as your captain levels and are up to your decresion which to open first. Crew skills stack. GET THEM LEVELING NOW.

1. Skill Allocation. Dont worry just yet where to put your points. At the start it really doesnt matter, stuff is starter and forgiving. Play and watch your performance to see where you want to put stuff. Different ships will dictate some of the crew skills you want, i.e. torp launch cool down useless to a Battleship. Tier 4 or 5 you will start to make some decisions as this is a fork point for the various class/tree lines.

1. Crews stay with the Captain, captains bound to a given nation's ships: Your IJN capt only gets to drive IJN ships

1. You do not have to buy the modules that you research to open the next Tier, merely research them. Nor is necessary to reseach everything to open the next tier ship. Its one line or branch, usually 3 modual "steps". Once you have a ship reseached you can then buy it and enjoy your new toy.

1. Mastering a ship is when all the moduals and ship(s) that you may/can fork too are researched. A mastered ship gives a bonus to xp and credits earned per match, for that ship only, and also allows you take all the xp from that ship and make it available for other ships (cost gold). How important? I have only one mastered ship, I did it cause it was fun to drive and it allowed me to help grind through another ship that was Not Fun.

1. You can add mods to your ship. Armour of different types and various ship ability altering mods, like ship speed or gun reloading speed are available from day one. They cost either credits or some cost gold. All of them decay over time ( the best is like 7 days) but are fully functional battle to battle for the duration. You start with one slot then open others with credits, each mod occupying a slot. Each mod type has corresponding "penalty" in ship speed reduction. Choose accordingly
3. IMO, all the classes are fun to play and serve a purpose. I have killed everything with everything( and visa versa). There is no best class, its your playstyle that dictates best. The Nations ARE different with respect to a given class. Look at the research trees to see whats what. Even still, it will take a bit to appreciate those differences.
5. Battles: Currently only one mode, general. The main goal is too kill the other guys first, Last team standing wins.
6. There are only a few maps, but starting postion does mix it up. Most of them have bases that battles pivot around.
8. Bases: Depending upon the map there are a number of different type of bases. The TWO main types are RADAR and AirFields. There are 3 things a captured base provides for its team. One is a field of vision around it. Bases are the main way of removing the FOG of the battle field. Second is the given bases function, i.e. a Radar base will provide a periodic ping to reveal enemy location on the map. Very Usefull. And Third a base can become a Teleport point. Beyond a the simple removal of fog, base function and teleport require a 50% cap to be enabled
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10. Captureing a base ( turn it your team color) is a done by Landing Craft, which all ships have. To capture a base, hover your mouse over the base, NOT the Island its on, and a red circle will light up. When your ship is inside( only need to be part way) Right click the base. You will automatically stop and begin moving landing craft to the base. Any ship can capture a base, some are just better at it than others. APA are the fastest, that is, there landing craft tick off the highest capture point per landing craft in the game. Destroyers are next.
12. A NOTE  ON BASES: Depending upon the map they are largely tactical in nature as to how important they are. There is NO Reason to capture every single one. Bases start out Either fully capped in your camp or Neutral. The vision they provide is probably the most consistant reason to capture one across the map types and is easily achived on a neutral base. Dont be afraid to stop and drop 5 or 6 lc on it if no one is around!!
14. VISION is king in the game. Nothing worse than being shot at and you cant see when to return fire. Scout planes are your friend and the enemies planes can be your biggest pain.
16. Planes become available in the game to Carriers at Tier 5 and then depending upon class of ship and nation, scout planes become availble at Tier 6. Destroyers and Submarines Do Not field scout planes
18. Anti Aircaft fire or AA. It takes practice to shot them down AND your guns have to have AA ammo. Not all ships/guns have AA ammo, However... there is small rudimentary auto machine gun aa that all surface ships have. It gets better as you move up in tier but is largely a AI driven self defense mechanism other than a usefull Fleet Support ability.
20. How To Shoot a Plane: A typical scenario will be a stationary target. It will have a small red circle on the water/land surface with a Vertical line going up and the plane on top of this line going in a small circle. The plane is going around the circle on the water, on the outside of it. Place your gun rectual outside that red circle and anticipate when the plane will be over your rectual. Fire. Practice. Destroyers have some of the best AA accuracy in the game and improves with tiers.
22. FLAGS: One player from each team is designated as flag, the have a little unique icon next to there name. The designated player has a supped up map icon with addtional features for bomb calling and recon. These functions are on a timer only start ticking if your team is in possesion of an Air Field. Flag status seems to be largely a function of capt level and not ship type.
24. Teleporting: you can move from one base to another as long as that base is 50% percent captured status. You must be completly stopped with no aircraft in the air. To do this, be at a base, stopped and a white "teleport available" section of your minimap will light up (outside ring 11 oclock). click that and map will open with availble destinations highlighted as blue circles. select one, then push the "go" button at the lower right hand of map.

OK, your Destroyer. All Ships have an Info Window. Right click your ship to familiarize you self with its features and install your mods. There is a slider here for amount of ammo types available to you, just HE and AA for destroyers. New guys.. There is Friendly Fire in the game: Dont go spastic and spam torpedoes please. You get Mines until Tier4 then you get swapped out for depth charges. The mines are really useless at this stage of the games development and just get in the way. Nothing worse that trying to dodge torpedos only to go over a friendly mine instead. You get torpedos out the gate, fun stuff and once mastered are deadly. NEVER FIRE them in your teams Back Field, you kill your mates that way. Your sonar and depth charges are submarine kryptonite. The Sonar is very RNG and can be frustrating. Spam this all you want :) Your depth charges.... you can set their explosion depth with the R and T keys. What depth? Usually your going to drop them once you have "pinged" a sub, that is a little red circle will appear on the water with a depth rating inside it, i.e. it will literally be either 1-5 or 6-10. You have to  guess where in that range of depth the sub is. A spot on depth set by you will kill the sub, one level off will do 50% damage. I usually run mine at 3 then adjust accordingly. A sub on the surface is at depth 0. A ghostly image sub is at depth 1. They are invisible after that. Surface guns will kill subs at depth 0 and 1.

Lastly.. you can sink any class/tier in the game. Period. Carriers and Subs hate you. However you need to learn how to lay torpedoes down on a moving target and HOW to fight stuff. Your going to get one shot by a BB broadside, or lose dueling most stuff for that matter, beyond another DD. Tier 10 DD run from Tier 4 BB, or rather.. they respect them. That being said there are lots of upper tier DD drivers who command respect and are KOS to folks. Enjoy