1: Be patient.
2: Take it slow.
3: Keep your shield up at all times.
4: BE GOD DAMN PATIENT.
5: Do not run through an area unless you've explored it before and know what to expect. Otherwise you're begging for an ass kicking.
6: While hard, Dark Souls, like its predecessor is fair for the most part. 90% of your deaths are your fault and yours alone and aren't usually the result of cheap bullshit, the game is a learning experience, learn from your screw ups and think how better to approach the situation next time.
7: The Capra Demon IS cheap bullshit however. You'll understand this point when you fight him.
8: Ideally, you want an idea of what your character is going to be before you get a decent way into the game, level your character accordingly.
Do you want it to be a slow, but heavy hitting, resilient, knight style character? Then pump your points into strength primarily as your damage stat, with the odd few points into dexterity for a couple really nice weapons, and then more points into things like endurance and vitality.
It's a logical process, faster, more nimble weapons require and scale with dexterity, slower, heavy hitters scale with strength.
9: There is almost always, always a shortcut back to the Firelink Shrine when you get close to a boss area, find it, rest at the bonfire there and save yourself a lot of time when you inevitably get your shit slapped the first time you fight it, it'll be a long walk back if you don't.
10: Humanity is not the same as being in human form, humanity, if I recall correctly, increases drop rates. Aside from that, it can be used to reverse the "hollowing", or undead form, as well as that, you can also use humanity to kindle bonfires for more Estus flasks every time you interact with that bonfire, the effect is permanent and can be done to multiple bonfires, you do however need the rite of kindling first.
11: Kindling bonfires also gives any other player online who rests at it an extra Estus flask, so if you've got humanity to spare, help a bro out and kindle a bonfire, because not only will it benefit you, but that extra Estus flask can mean the difference between beating a boss or getting beaten by it for that person.
12: Continuing with the topic of humanity, it's easily farmed from, curiously enough, rats in the linking area between the Undead Burg and the Undead Parish. Additionally, you can only summon other players to help you if you're in human form, so taking some time out to farm humanity here can be beneficial.
13: Calm your tits if you die, all is not lost, you can return to the point you died at to regain all your lost souls and humanity, but if you die before reclaiming it all, consider it lost.
Now for a little combat oriented stuff.
1: While blocking in combat is always beneficial, don't forget to drop your guard now and then when your stamina is low, your stamina recharges MUCH faster when your shield is down.
2: Drake Sword, bow, arrows, dragon's tail, underneath bridge. You do the math, insane weapon for practically no risk which slaps shit hard for a while but doesn't scale with any stat, meaning it sucks balls when you get to a high level. Worth getting, it'll make your life so much easier.
3: If guarding enemies are getting you down and you're feeling a bit impatient, moving the left stick forward and pressing R1/right bumper at the same time performs a kick which staggers your opponent, use this to your advantage. It can also be used to kick particularly irritating enemies from great heights.
4: In the same vein, forward and R2/right trigger executes a jumping lunge attack, it's risky, leaves you open to a very easy counter attack by faster enemies while doing it, but it can hit like a truck and end a fight very quickly, using it is entirely at your discretion and entirely at your own risk.
5: Forget parrying, just don't bother with it unless you're absolutely, 100% sure you can successfully pull it off. If successful, it may impart you with a one hit kill and an absolutely bitchin' animation, but without a lot of practice, it's too much of a high risk move to use regularly.
6: Two handing a weapon generally isn't worth doing unless it grants you some special ability with that weapon, like the Drake Sword and its shockwave attack. It's almost always preferable to one hand a weapon and use a shield.
7: Compared to Demon's Souls, rolling isn't nearly as effective as it used to be. There's a clear difference between the two games in that armour and straight up shield usage is miles more effective than it ever was. Plus, Dark Souls features more enemies than I can count that seem to have stupid fucking moves that track you and hit you even if you roll out of the way. Though dodging IS still useful in a pinch, don't forget it exists.
8: Pyromancy is broken, like, hilariously so. Abuse this for an easier time in general.
And that's all I can think of at this moment in time, hope it helps.