Dark Souls II

Character Generation

Starting characters largely are a lot weaker than in the first game. One of them can't even properly wield their weapon in one hand. Fortunately, you can fill in the gaps in your stat spread and equipment quite quickly.
From the available starting gifts, the Healing Wares gift is the most helpful to a new player.
There is no pyromancer start this time, but you can acquire a pyromancy flame and find a trainer fairly early.

Estus flask shards give you more uses of your estus flask when turned in to the Herald. The first available shard is hidden in Majula and can be acquired at the start of the game.
The first two areas accessible out of Majula are the Forest of Fallen Giants and Heide's Tower of Flame. The active enemies in Heide are much more intimidating than the enemies in the Forest, but the areas are roughly balanced. If you get stuck, try going down the other route for a while.
There is a merchant who moves to Majula after you beat the boss near where you meet her. Once she's done this she offers an infinite stock of basic lifegems. These are an excellent way to heal up between fights, saving your Estus Flask uses for healing swiftly in combat.
The armor merchant gains more stock when you've given him enough souls. It can be worth throwing some at him even if you aren't interested in his starting wares. He will also sell some boss armours once you've defeated them.
A pair of binoculars hidden in Majula can be used to aim spells in first person and survey the local scenery.

Be aggressive without being blinded to your surroundings. The game likes to throw mobs of weak monsters at you that can overwhelm you if you don't thin them out as they come. The game also really, really likes ambushes.
To revert hollowing, simply use a Human Effigy from your inventory. Completing your duty as a summoned cooperator will also reverse hollowing.
If you're unhappy with your past leveling decisions or simply need to adjust your build because you've run into a wall, you can reallocate your attributes by giving a Soul Vessel to one of the old firekeepers in the starting area.
Most weapons are perfectly serviceable for completing the game. Don't get hung up on acquiring the optimal equipment your first time through.
Don't try to use Every Magic your first time through. If you decide to cast spells, stick to one type.
Strike (i.e. blunt) damage is very strong in this game.

Weapon reinforcement is extremely important, and you should have your main weapon upgraded as high as you can at all times.
Keep a backup weapon, ideally one that possesses a moveset and physical damage type different from your main weapon. Weapon durability is pretty low in this game, and damaged weapons do a lot less damage.
If you are a caster, you should reinforce your spellcasting tool to make your spells stronger. Infusing them with the appropriate element will also empower your spells.
You can upgrade armor but this is not recommended, at least until you have the ability to purchase infinite titanite.

Two-handing a weapon effectively doubles your strength stat for the purpose of meeting weapon stat requirements and calculating damage.
If you have a weapon in each hand and your Strength and Dexterity equal to 1.5x the the highest of the weapons' requirements, you may Power Stance them. To enter Power Stance, hold down Triangle/Y as though you're attempting to two-hand your left-hand weapon. Some weapons can't be stanced together, or at all.
Unlike in the first game, your rolling speed is always the same up until 70% Equipment Load when it turns into the clunky "fat roll". Equipment Load still governs how fast your Stamina regenerates and how far you can roll.
Also unlike the first game, your i-frames are not controlled by your roll speed at all but rather by a secondary stat named Agility. It is increased primarily by putting levels into Adapatability, but Attunement also affects it to a lesser extent. 99 Agility is usually considered the goal to aim for.

Prism Stones, Smooth and Silky Stones, and Petrified Somethings can be exchanged for items with a pair of talking crows by leaving (not discarding) them in their nest in Things Betwixt. Petrified Somethings yield the rarest items.
Exhaust all dialogue with NPCs when you meet them, to avoid missing things and to move them to Majula if they are so inclined. Many NPCs may also give you items if you talk to them again after having met a certain prerequisite, most commonly after you've bought enough stuff from them.
Barring a few obvious exceptions, secret doors are opened with the loot/talk button rather than by attacking the wall like in DS1. A few suspicious-looking walls can be destroyed by hitting them or using something found in the nearby environment.