Just lots of trial and error.
Play it safe rather than sorry, and be wary whenever you meet anything new, especially bosses. Expect to die, a lot, but you will get into it. Farm in places like world 4 for souls. Once you get used to the skelies there it goes fast. Also read up online, there are a LOT of things this game does not explain to you.
I love this game because how hard and unrelenting it is. Something so exhilarating about facing the challenges in this game and overcoming them. This game is like a Thriller Horror RPG.