In this day of self-publishing and e-publishing, I have noticed a relaxing of the proper use of point of view. I've read a number of books where the author switches their POV character back and forth at random. This is easy to do. I have done it myself. So a review of the basics will be covered here.
As we all know, there are three basic POVs which a writer can use: First person, third person, and omniscient. The first person is the "I" voice. This is written as though the narrator were speaking to the readers. The first person narrator is one of the characters, not the author. This POV can give the reader a good deal of intimacy with the viewpoint character as it allows the reader to get into the head of the viewpoint character and literary allows the reader to see the world through that character's eyes. This first person POV character has to be a strong character in order to keep the readers interested because he will be limited to only what he knows, sees, or hears directly or immediately. This can prove to be very limiting as the book will be through one character's viewpoint.
All narrative summary is written in the omniscient POV. With the omniscient POV you do lose the intimacy and warmth that you have with first person POV. The omniscient POV is the author speaking.
The third person POV is, of course, the one most authors use and the one that most publishers seem to prefer. It has the most advantages because it allows the readers both intimacy and perspective. Also, with the third person you can move from character to character, giving the reader the ability to view the story from different angles. The biggest problem authors have with this POV is being consistent throughout each scene. It is very easy to change the POV character within the same scene without even realizing it.
Another problem with third person POV is that some authors cannot resist the temptation of having too many POV characters, and they ten to switch between these characters so frequently that the readers lose interest and are apt to not finish the book. It would be more effective to stick with a single POV and show the other characters' feelings through dialogue and actions or, at best, keep the number of POV characters to no more tan two or three. And if it is necessary to change your POV character, you need to end the current scene. You do that by inserting a line space (this can be done with asterisks or simply spacing down four lines) and starting a new scene from the POV character that you need. Also, be sure to establish who the POV character is in the first paragraph of the new scene.
Remember that a POV falls between two consecutive lines of dialogue. A POV does not particularly mean a break in time.