POV wasn't something I ever really thought about before I started writing. Sure, I knew that a story was generally told from a certain character's POV, but I had no idea what that really meant. As was evident by the early drafts of my first book.
My first book was a POV NIGHTMARE. I didn't wait until a chapter or scene break to jump into another character's head. Oh no. I would jump from head to head without a care in the world. I once had four POV's going on in the same paragraph.
Luckily, the wonderful, kind, and oh-so-patient members of my first crit group pointed out the rules about POV. One of them told me to think of it like this: Pretend there is a camera on your MC's head. You can't see, hear, smell, touch, feel, or know anything that your MC doesn't. If you need to be in another character's head, insert a scene or chapter break and go for it. But don't hop around.
Now, I've read many books were the POV hops from character to character mid-page and sans scene/chapter break. It can be done if it's done well. But for the most part, when the POVs go hopping, it does nothing but confuse the reader.
Try not to do it :)
How are you with POV? Was it something you knew to do well right away, or were you a POV nightmare like me? :D