Before you even create a character, you should probably understand the basics of the game and how classes work. Though other MMOs rely heavily on the "holy trinity" of tank, damage-dealer, and healer, in ESO, every class is designed to have some competence in anything you want. It's a bit of a different spin on the traditional class system that most MMO players are used to.
At first, you can select between four classes -- Dragon Knight, Sorcerer, Nightblade, and Templar. As a general rule, these classes are similar to those in other games respectively -- warrior, mage, thief, and priest. But again, ESO doesn't prescribe to the typical setup, so all four classes can tank, heal, or do damage. The reason this is possible is due to the dynamic weapon and armor experience system, as well as guild and faction skill trees that unlock new adaptive abilities. For instance, if you're a Dragonknight, you're generally adept at hand-to-hand combat, but if you want to heal, you can buy and equip a healing staff and gain access to a number of powers that can restore health to you and your party. You're also free to equip light, medium, or heavy armor and put points into skills that complement your playstyle. Take a few minutes to scan down the entire line to see what suits you best.
To further customize your character you'll also have access to the Fighter's Guild tree, as well as the Mage's guild, and a few other factions -- you can gain access to these by dropping by both guilds in your starting town and grabbing the quests. If you're a Templar or Sorcerer you can put some points into the Fighter's guild tree to increase your physical damage, or vice-versa for the Dragon Knight and Nightblade in the Mage tree. Practically everything is viable for leveling, and there isn't any real "wrong answer," unless you're putting tons of points into powers that you never use.
As a rule, it doesn't matter what race you pick, but all of them have special racial abilities that complement a certain playstyle -- like extra power with two-handed weapons, or swords and shields, for instance. While it's not required to match your race up with your style to succeed, if you're a min-maxer and a competitive player you should think hard before pulling the trigger.
If you've pre-ordered the game or picked up the Collector's Edition you'll be able to choose your faction -- otherwise it is dictated by your starting race. The factions basically just dictate your questline and the area you start off in, with the Ebonheart Pact sending you into Morrowind, and the Aldmeri Dominion and Daggerfall factions sending you into the Summerset Isles and High Rock. They're generally all the same, and you should pick whatever starting area resonates with you if you're a fan of the series -- having said that, I've found that Daggerfall has some of the most straight-forward quests.
If you have the Imperial Edition you can head to the stables right away and pick up your first mount (a horse) for one gold. Open up your map and look for the white horse icon once you've completed the opening area. Note that every player can just buy a mount whenever they want once they have the scratch, and horses can be fed roughly every 24 hours to increase their stats, such as speed or resilience. Maybe horse armor will be an option down the line!
Now, you're going to want to do the standard operating procedure for every MMO -- grab every single quest you can find. In Elder Scrolls Online quest XP is massive, and grinding out dungeons or random mobs isn't nearly as effective as completing the main storyline or sidequests. To make sure you're always scanning for new quests, look up at the compass at the top of the screen and pay attention to black arrows -- especially glowing ones. Those indicate new quests, and you should head for those immediately.
When leveling, you'll have access to three skillsets based on your class, as well as your weapon skill tree, and faction sets as you unlock them. Cycle through all the skills, decide which ones are the most important to you, and equip at least one from each of those trees while leveling. Even if you don't use an early skill in a tree, the mere fact that you have it on your hotbar helps that entire tree level up faster, which unlocks higher level abilities. You don't need to bust out the graph paper, but planning ahead helps.
Sometimes you'll have to fight very tough enemies on your own, and occasionally they'll beat you into a pulp. Don't just keep rushing in with the same strategy -- experiment with different builds and abilities, and try to equip an ultimate ability to supplement single target damage. You can also equip your strongest abilities that use mana and stamina, rush it, spam both meters, then use a recovery potion to renew your most precious resource. Farming enemies to power up your ultimate ability to use in a boss fight is also key to bursting your way to success. Speaking of ultimates, always make sure to grab one as soon as you can early-game, as it can help you out of a jam more than anything else in the game.
When you hit level 10 you'll be able to PVP, which takes place entirely in the land of Cyrodiil -- which some of you may remember from Elder Scrolls IV: Oblivion. To jump into the constant tug of war between all three factions, open up the menu and select the battlegrounds option, select a "campaign" (a server, basically, which all have different outcomes and results), and queue up. After a short period of time you'll teleport to the battle, at which point you should grab every quest in sight and team up with fellow players to complete them. Do this periodically if you have trouble leveling, but don't count on it as a primary means of working your way up the level ranks.
Once you've gotten accustomed to the leveling process, you'll start to soar past 10, which means you're ready for your first dungeon (instance). As soon as you hit level 11,three instances will pop up on your group finder tool, which allows you to select your role and match yourself with another party of players. There are three dungeons that unlock at this early stage -- Banished Cells, Fungal Grotto, and Spindleclutch. Make sure to do each dungeon at least once, because each one has its own questline that gives a massive amount of experience. You can grab the quest while inside the dungeon for the first time, and you can teleport to players by opening the party menu, right clicking a member, and selecting "teleport to player." Note that although you can technically use the matchmaking tool at 11, many parties or group leaders might prefer you to be at least level 12, even though you could easily do them at 11 -- go figure. If you're looking to practice your dungeon-running skills I recommend Banished Cells, as it's the easiest one. Basically all you need to remember is to play your role, stay out of fire on the ground, burst damage and kill healer enemies first, and run out of red circles when boss characters charge up a power.
After you've gotten your feet wet in the game's dungeons, continue questing and repeating the process, queuing up for instances when they unlock in your finder tool. Repeat that sequence of events until you're level 50, at which point you'll be ready for endgame Veteran content. Elder Scrolls Online has a longer leveling process than some other major MMOs on the market, but as long as you aim to double-check your achievement list to make sure you've done every quest in an area, you shouldn't have too much trouble. If you're craving functionality that doesn't come standard with the game, note that Elder Scrolls Online supports mods and add-ons, which can be grabbed from various MMO sites like Curse.com.