Point of View and perspective are actually two different things, but the distinction can be confusing. Until you are sure of which is which, it's hard to know when to use each.
Simply put, perspective is who tells the story, and point of view is how they tell it. Still confused? Here's what I mean:
Choosing a perspective means choosing a character to tell the story. Stories are generally told through the eyes of a single character, and although that's usually the main character, that isn't always the case. The Sherlock Holmes tales, for instance, are always told from the perspective of Watson, Holmes' assistant.
Point of View
Point of View is a little more difficult to describe. Selecting a point of view means deciding how to tell the story. Point of view is traditionally divided into four methods:
First person--This is used very frequently in young-adult fiction, somewhat less frequently in mainstream fiction. The story is told as if the perspective character is telling it directly. The major pronoun here is I.
Second person--This is probably the least used point of view in mainstream fiction. It is occasionally used in young adult fiction (the Choose Your Own Adventure series, for instance). The story is told as if it is happening to the reader. The major pronoun here is you.
Third person, limited--The story is told as though by a narrator, but the narrator only knows the thoughts of the main character. The major pronoun here is He/She. This is probably the most-used point of view in modern mainstream fiction.
Third person, omniscient--The story is told as though by an all-knowing narrator who can describe the thoughts and actions of all characters.
Putting it Together
That, in a nutshell, is perspective and point of view. Taken separately, they are easy enough to handle. It is when you work with the combination of both that things get interesting.
Implied in the idea of perspective is the concept that the perspective is fixed. Traditionally this is so, and yet we have all seen examples of works where this "rule" is broken, and the perspective changes from chapter to chapter. (My personal favorite example of this is Phantom, by Susan Kay)
The idea of a fixed perspective works particularly well with first and second person points of view. Third person limited also seems made for fixed perspective. From those points of view, the perspective is inherently fixed; there is no possible way for one character to know the thoughts of another.
There is also no possible way for that character to know about things that happen when he/she is not around. This means you really can't convincingly include scenes that don't include your perspective character, no matter how important they are. This can be a major drawback in some stories!
Third person omniscient almost makes perspective optional. It's so easy to just switch from one character to another--it's really too easy. If you're using third person omniscient, you must be very careful about when you switch perspective and how you handle it, or you will end up confusing your readers. Third person omniscient opens up wonderful opportunities for creativity--or disaster. Make sure that when you switch perspectives, there is a reason for it, and that your reader will be able to follow the shift. There is nothing more irritating that starting to read a chapter when you don't have any idea who's telling the story!
First person, however, while seemingly restrictive, actually offers an interesting possibility. First person is really the only way to convincingly carry off what I like to call "revolving first person"--deliberately changing the perspective from chapter to chapter so that you have several characters each telling their part of the story. This can be really fun to do, but must be done with care, or you will run into the same problems third person omniscient can lead to.