Pokey: Dark Souls is fairly melee-focused. As Botch notes, a very magic-heavy build will be a problem, especially early on. Some magic helps; but my experience is that you're going to be doing a lot of hand to hand combat. My own playthrough build was a Sorcerer, but the sorcering took a back burner to swordfighting. Archery is still available and works the same; again, however, it would be hard for an archer starting out - arrows cost more than the souls you'll get from kills early on.

Humanity is very important. You can earn it by invading other players and defeating them, but it's more common to be awarded a point for defeating X number of monsters in the same region. Loose Humanity in your pool - the large number next to your health bar - is dropped with your souls when you die, so be careful about carrying a ton of it loose.

The more Humanity you have in your pool, the more item drops and lucky events will occur. You're also more likely to be invaded. If you die while carrying a large amount of loose Humanity, you will spawn a Vagrant - a demon that randomly invades another player's world.

You can also find (and buy) Humanity in little vessels. Rats, for some reason, often carry it. It's preferable to carry it this way because you don't drop it if you die. Then you can just "use" the vessel to crack it and add a point of Humanity to your pool.

What's it for? Two things: you spend a point of Humanity at a bonfire to reverse your Hollowing, which essentially brings you back to life. There's no "soul form" this time around, and no health penalty for being Hollow, but while you're Hollow you cannot summon help from other players or get invaded. You're also grody to look at and some NPCs dislike Hollows.

When you are NOT Hollow, you can burn another point of Humanity to Kindle a bonfire, which doubles the Estus you receive from camping there - ten doses instead of five. That's pretty huge. Note that any bonfire with a living Fire Keeper (this includes Firelink) is already Kindled, so you can camp there and get ten doses any time you like.

There are indeed many shortcuts, but they always have to be opened by going the long way at least once.

I've said it before but I'll say it again: if Demon's Souls was brilliant, Dark Souls is an absolute, unadulterated masterpiece. I'm jealous of you guys. Have fun!

The Cemetery is not for you yet - low level characters will get lit up down there. Bear in mind that some of those skeletons cannot be killed without a holy weapon and they'll chase you for miles and miles. If you do visit, just dart down to loot bodies and scamper back up to Firelink. The best place for newcomers to begin is the Undead Burg, up the narrow steps and through the aqueduct.

Pokey, many rats will poison you with their bite, but that one's not too bad. It's worth it to kill him every time, as he might drop humanity. Rats carry a lot of humanity for some reason.

Covenants can impact your game a lot or a little. The Way of White, which is the first one you found at Firelink, slightly increases item drops and improves your chances of seeing Summon Signs to get help later on. Others are available elsewhere, through other NPCs, assuming they like you and you answer their questions correctly.

You can always quit a Covenant to join a new one, usually without penalty. However, Covenants do have rules. If you break those rules you earn a level of sin; the more sin you've got the worse things tend to go for you. You can only clear out sin by purchasing absolution from a specific character who charges a great deal for the service. If you're not interested in doing too much with Covenants just stick with the Way of White; it's not very interesting but it pretty much leaves you alone. Other Covenants include the Forest Hunters, the Daughter of Chaos, the Warriors of the Sun, the Dragon Covenant, etc etc etc. Each brings specific benefits and certain requirements you're expected to fulfill.

Covenants are one of the fascinating aspects of Dark Souls that make the game so immensely huge and freeform. You can ignore them completely if you like, or get very heavily into Covenant questlines.