So I've seen World of Tanks mentioned in another thread recently and I decided to do sort of an intro thread for the game because it's not very heavily marketed but is nevertheless pretty fun, if you're into that kind of gameplay.

http://www.youtube.com/watch?v=THn_FZAxvuQ&hd=1

So, what is it?

World of Tanks is probably best described as Counter-Strike with Tanks and persistancy thrown in. There are two main parts of the game: the Garage, and the Battlefield. I'll go over the Battlefield first, because that's where all the blowing up of stuff is.

The game is Free to Play. There is no "subscription" system. Premium features use Gold currency instead of regular currency, and the Gold is bought with real $. The current exchange rate is 250 Gold for $1. Here's stuff that you can do with Gold:

-Upgrade your account to Premium for a set duration (1 day, 3 days, 1 week, 1 month). 1 month costs 2500 gold, so $10, and is the best overall deal in terms of Gold per $. The benefits of a premium account are 50% more XP earned, and 50% more Credits earned (more on the uses for these in the Garage section).

-Buy Premium tanks. Usually each nation has a couple of Premium tanks. These are more flavor, the best tanks at the moment are not premium. They are good at what they do, but they're not the "top" tanks. The main benefit is that it's easier to get them as there's no research requirement. They can be pretty cheap as well, one of the medium tanks for Germany is 1000 gold ($4).

-Convert XP to Free XP. Each vehicle has its own experience pool that can only be used to research upgrades on that vehicle. 10% of the normally earned XP is automatically added to your Free XP pool. This pool can be used to research on any vehicle. When you research everything on a vehicle, it still gains XP from battles, and you can choose to convert it to free XP. 25 xp costs 1 gold to convert to Free XP. The main use for Free XP is to skip "over" a vehicle in the tech tree (more in the Garage section).

-Form platoons and companies. Probably the worst part of the WoT F2P system is that you can't queue to a battle (there are no servers, just instant matchmaking) with your buddy without one of you having a Premium account which allows you to queue as a team.

So, as you can see, there's really nothing in Premium that gives a competitive edge to a player. The premium tanks are the closest thing, but they're not the best tanks in their classes, so buying one won't give anyone an edge. For the most part, Premium just lets you move up tiers faster.

The Battlefield

Battles in World of Tanks are 15 vs 15 on any one of 10+ maps. Each team starts at their side of the map, though not necessarily their base. The goal of the match is either to destroy all the enemy tanks, or capture their base. Destroying tanks is self-explanatory, and capturing the base is accomplished by staying in the capture zone while the capture bar fills. The more friendly tanks in the capture zone, the faster the capture. A few seconds after the bar reaches 100%, the capturing team wins the map.

There are currently 3 nations in the Open Beta version of WoT. USA, Russia, and Germany. Each side has an assortment of light tanks, medium tanks, heavy tanks, tank destroyers, and SPGs (Self-Propelled Guns, basically very long range indirect fire artillery). 

Tank controls are what you're generally used to in FPS games. W/S/A/D moves your tank, and mouse aims your cannon. Note that even though historically tanks had more than one weapon (and these are on the tank models in-game), you only ever shoot your main cannon. For vehicles with a turret (light, medium, heavy tanks with a few exceptions like the US M3 Lee), the turret automatically rotates to your mouse pointer - meaning, there's no separate control for turret rotation on top of tank movement. For vehicles without a turret (Tank Destroyers, SPGs), if needed the vehicle rotates to your mouse pointer if you aim outside of the frontal cone.

The tanks all have their own feel and handling, as you would expect. Movement is NOT arcade-y. Each tank has weight, and its treads and engine (more on this in the Garage section) determine its maneuverability and speed. No two tanks handle the same. Some have faster top speed and accelerate faster, but they lose a lot of speed on turns. Other tanks have lower top speed, but are more agile and turn faster with lower speed loss. Light tanks can zoom up hills fairly well, while slow and bulky SPGs turtle crawl up them. Turret rotation also differs. Big heavy turrets turn slower than lighter ones, so light tanks can most certainly run circles around heavy tanks and it will be very hard for the heavy to hit them (even though the light won't be able to do much to the heavy, except possibly knocking out its treads with some well-placed HE rounds).

Each tank also has crew and "subsystems", if you will. You can blow out treads. You can destroy the engine. You can destroy the cannon. You can injure crew. Your crew is what determines how well your tank performs. When you get a fresh tank, your crew is fairly inexperienced (though you can spend money to train them), and as you fight they will train up to full effectiveness, at which point you can train them with extra abilities (better camouflage, faster repairing, faster firefighting). Your crew is responsible for manning your tank. You have loaders, gunners, commanders, drivers. If you lose your loader, you will reload slower. If you lose your gunner, your accuracy will decrease. If your treads bet blown out, you will fix them but your mobility will be decreased. If your engine gets smashed and your tank catches on fire, you will repair it and put out the fire, but you will take extra damage from the flames and your speed will be reduced.

You can transfer your crew from tank to tank, though they lose some effectiveness - transferring between tanks of the same type (like Tank Destroyer to Tank Destroyer) loses 25% training since they're not used to the new vehicle, and transferring between vehicles of different types (Tank to SPG, for example) loses 50%.

You can recon, and you can hide, and you can flank. Each tank has a radio system, which is used to relay information on contacts automatically to your teammates in radio range. One of the jobs of Light tanks is to scout ahead, they're small and hard to detect (especially if stationary in a big bush), and with a good radio they can pick up contacts and light them up for your allies in range. The tank cannon ranges are always higher than detection ranges, so a Light scout ahead of your main Heavy/Medium tank group will allow them to shoot farther than they can normally detect. Depending on your tank, you can also hide. Big bushes that cover your whole tank make you hard to detect from the distance, unless you start shooting out of it. As you can imagine, some of the bigger tanks aren't much good at hiding and no bush is going to hide their massive size. Each tank also has its own weakpoints. Shooting the front armor of a heavy tank is pretty silly, shooting the back or the treads is much smarter! Aiming is manual, and your reticle is color coded depending on where on the tank you're aiming. Green means you've got a damn good chance to penetrate armor (usually every tank's treads are pretty vulnerable, for example), Yellow means you might penetrate, and Red means you better try aiming somewhere else unless you like wasting ammo. Armor slope isn't taken into consideration. If a vehicle has sloped armor, and a shell hits it at a bad angle, it has a high chance to bounce off and not penetrate.

I think that about covers the combat mechanics at a glance.. on to the Garage

The Garage

The Garage is where you outfit, research, and buy your tanks. Each nation has a tech tree with tanks leading to other tanks. As Germany, you can't get into a Panther II (tier 9 Medium tank) without researching the Panther. Or a King Tiger without researching the Tiger. The dependancies are not always linear, and the trees can jump around. For example, the German Pz III medium tank can lead either to Pz III/IV tank which continues down to the Panther II, or to the Pz IV which continues down to heavy tanks and ends at the Maus. You're never excluded from what you can pilot, as long as you have the time, xp, and credits you can unlock every vehicle in the game. So even though you mostly pilot Russian tanks there's nothing stopping you from starting to work on the USA tech tree.

Each tank has its own research tree, where you can unlock various components. These are generally better treads, better engines, better radios, better turrets, and better guns. You get a "stock" tank when you buy one fresh from the store, and you use XP earned in battles while in that tank, or Free XP, to research upgrades. After you research an upgrade, you are able to buy it and fit it to your tank (assuming you meet the requirements, weight and turret type if mounting a weapon).

Treads - improve your maneuverability and load limit.
Engine - improves your top speed.
Radio - gives you a larger radio range so you can relay contact information and receive contact information from allies. If you're out of radio range, you can't see what they see on the minimap.
Turret - usually bigger turrets are needed to fit the bigger guns available for a tank, and they also tend to have more armor.
Gun - self explanatory. Most tanks have more than one gun that they can mount. The StuG III Tank Destroyer can either mount a highly accurate 75mm cannon for good long range shots, or a very inaccurate 105mm cannon that deals massive damage if it does hit, instead.

You need credits to buy the part after you've unlocked it, and you also need credits to repair your tank after a battle and buy more ammo. 

http://www.youtube.com/embed/BolSW2zPQwo?hd=1

That about covers it, I think. I'm having quite a bit of fun with the game, and will definitely play it on launch.