I've got a few tips (Okay maybe a slight crash course):
-If you're playing on PC, get a controller. This is not a game meant for mouse and keyboard.
-Following on from the previous point, download DSFix. It'll make the game actually run.
-DON'T take the Master Key as your starting gift. Your first playthrough should be used to get yourself acquainted with how all the different areas are connected. The Master Key kinda fucks this up since you can open certain early mid-game shortcuts on your first run through the first area. I would take the Old Witch's Ring since that will give you some insight on a side story later on.
-Stats are pretty important to know. There's a button in the stat menu that will explain briefly what each stat does but I'll run through them now to avoid later explanation:
Vitality (VIT) - Increases max HP. No points are wasted here.
Attunement (ATT) - Increases the number of spells you can have equipped at any one time. You can equip two copies of the same spell to give yourself multiple uses.
Endurance (END) - Increases max Stamina, Equip Load and Bleed resistance. No points are wasted here.
Strength (STR) - Increases weapon damage based on the weapon's STR stat scaling which will be ranked from F at the lowest, to S at the highest (F, E, D, C, B, A, S).
Dexterity (DEX) - Same as Strength, but with DEX. It also increases casting speed for Miracles, Sorceries and Pyromancies.
Resistance - That stat that idiots put their levels in. Don't level it up.
Intelligence (INT) - Like STR and DEX for Sorceries. Also increases the power of catalysts (staves basically), causing your sorceries to become more potent.
Faith (FTH) - Basically intelligence for miracles. Also increases Magic Defence.
Humanity - You can't actually level this up with souls. You gain levels by consuming Humanity items or by chance by killing an enemy in an area where you haven't defeated the boss. You lose Humanity upon death, as with souls, but it can be recovered from where you died. It increases item drop rates, boosts all defences and curse resist and increases the damage of weapons with humanity scaling, although you don't gain any benefits from this or item discovery past 10 humanity.
Poise - Pretty much your resistance to being staggered by an attack. It's governed by the armour you're wearing. You can think of poise a bit like having an invisible bar like HP that depletes with each hit within a certain time period. Different weapon classes have different values for, what's known as poise damage. You should always try to have at least some poise, as having no poise will often times end with you stun-locked and killed.
Equip Load - The total weight of the armour and weapons you have equipped. This affects the speed of your rolls and sprinting, and how long you remain invincible whilst rolling. There are three tiers to rolls: The light roll is achieved by having an equip load less than 25% of your maximum. This grants the quickest, longest roll with the most invincibility frames. Mid rolls occur between 25 and 50% of your max equip load and are the roll you'll most likely be doing on your first playthrough. The slow or fat roll, as it's known, is the slowest roll with the shortest distance and fewest invincibility frames. It occurs above 50% maximum equip load.
-Classes aren't fixed things, but your choice does matter in the early game:
Warrior is probably the best class to start with on your first run through due to their high starting endurance, high strength and dexterity, a shield with 100% physical defence (meaning you take no damage from blocked attacks) and the Longsword, which is quick, combos well and has great moveset.
Knight is good for early tanking due to high defence and poise with the starting armour set, 100% shield (like the Warrior) and high starting vitality. You can also use Knights as a jumping off point for miracle/faith weapon builds do to their above average starting Faith stat. Other than that, you're probably better served picking something else. Their middle-ground endurance and heavy armour means they're slow and cumbersome and their mediocre Str and Dex means you have to put more points into those stats early on to use certain weapons, rather than Endurance, which is arguably more important to the Knight.
Wanderer is an okay starting class, but it requires a bit more skill to use. They focus very much on mobility with their light armour, low vitality and Scimitar, which is a very quick weapon with a somewhat low reach that is a beast against unarmoured enemies with no or low poise. They have high starting Dexterity, making them an okay choice to build a Dex character off, although the Hunter is the better class overall for that. The Wanderer also has above average Intelligence and Attunement stats, which allows them to use sorceries as well as melee.
The Thief is essentially a step further from Wanderer. They have higher DEX, FTH and INT at the cost of even lower VIT, END and STR. They start with the Bandit Knife, which is quick and builds up Bleed, which causes a huge amount of damage at once when it overcomes the enemies Bleed Resist. This makes the Thief useful against larger, slower enemies at the start, as they can use their superior mobility to dodge attacks and get in enough damage to cause the opponent to bleed out.
The Bandit is the go-to base for most STR builds. They have very high base VIT, END and STR, so are able to take and dish out damage very easily. The high VIT and END also means you can focus on putting your first three or four levels into STR and DEX in order to wield some powerhouse weapons early on such as the Zweihander and Claymore. This isn't necessary though, as their starting weapon, the Battleaxe, is an early game powerhouse in itself. It has high base damage and does an incredible amount of poise damage for an early game weapon, making it very useful against early toughies. The starting shield is also very good. It has 100% physical defence as well having defence against poison and toxic, which ends up being the source of much frustration and ire later on. The major downsides to the class are the low defence given by the starting armour set (although it is light, allowing the Bandit to light role right off the bat) and the Battleaxe's lack of ability to combo attacks, making it slower and more cumbersome than a sword.
The Hunter is easily the best class to build a DEX build off of. They have the same base DEX as the Wanderer, but with 2 more points in STR, alleviating the need to level it up early on for certain weapons. They also have higher VIT and END, making them more survivable and able to equip more earlier on. They also start with a bow, which is helpful in some cases.
The Sorcerer is pretty much a dedicated, well, sorcerer. They start with high stats in INT and ATT, and above average DEX, as well as a catalyst and the Soul Arrow Spell. This is at the cost of pretty much everything else though, so watch out.
The Pyromancer is another really good starting class. They start with a Pyromancy Flame, which allows you to cast Pyromancies, and the Fireball pyromancy, which doesn't have any stat requirements, like all pyromancies, which is huge in the early game as the early bosses are weak to fire damage. It's recharged at the bonfires, making it essentially a reusable firebomb. Best of all, you avoid the pain and misery you would otherwise have to go through to get the Pyromancy Flame. They also start with decently well rounded stats, a fairly okay starting weapon, and a very good starting armour set for fire and poison resistance. The only problem is the crap starting shield which should be replaced as soon as possible. A good choice is the Wooden Shield found near the start of the Undead Burg right after you arrive at Firelink Shrine.
The Cleric is pretty much the Faith specialist, although they are pretty well-rounded in their other stats. They start with the Canvas Talisman, which is a decent early game Talisman (the Faith version of a catalyst or the Pyromancy Flame), and the Heal miracle, which can help if you run out of Estus flasks in the middle of an area. Just be aware that there are very few offensive Miracles, so this class can't really be played like the Sorcerer or Pyromancer. Another weapon is pretty much required.
-Parrying is one thing that isn't explained as well as it really should be. The timing is key. In order to parry an enemy, they have to be humanoid, no larger than a Black Knight, and must be wielding a weapon. You must also be on the same level as your opponent and within punching distance. Basically just get as close as you can. The best way to get the timing is to look at the enemy's HAND, rather than the weapon. Parry as soon as the hand moves to strike. It'll take some time to get it right, but you will eventually.
-Upgrading weapons is more important than levelling up scaling stats like STR and DEX. The increase in damage is greater and the souls for levelling STR or DEX can go into the more important VIT or END.
Holy shit. That was longer than I was intending. Hope that helps.