Yesterday I talked about point of view and how everything needs to be filtered through the POV character. One way to check whether you’ve wandered away is to consider the subject scene as if it were written in first person. That will usually identify anything that doesn’t belong.
If you’re having a difficult time getting a grasp on POV, perhaps writing in first person will help you get a better feel for it. However, that can be limiting, depending on the story. I would have a very difficult time writing strictly from first person, though I know of at least one very skillful author who has her protagonist’s scenes in first person while other characters are written in third person.
It’s okay to tell your story, or sections of it, through the eyes of different characters. However, IMHO, these should be as separate sections, not all run together, which would constitute omniscient POV. Some books work in that mode, but if you really want your reader to relate to your characters, it’s best to give them their own voice in their own sections or chapters. Otherwise it can get confusing and far more difficult to get into their inner thoughts and feelings.