Depends on what kind of play style or build you like. I have invested most of my points in Vitality and Stamina so I can feel comfortable with melee and have a very high equip weight.
Only put points into dex/strength if you are using a weapon (or plan on using a weapon) that scales with those stats. Since I'm using lightning spear, my str/dex doesn't really matter.
If you're a magic user put your points into faith OR intelligence (there's a catalyst out there that lets you castle miracles based on int, for example).
Build up what you need to use the weapons you like and tailor to your play style.
I think it's worth plugging away at Demon's Souls a bit longer before you dive into Dark Souls. It's a beautiful game with many improvements, but it's considerably more difficult.