Point of view, or the perspective(s) writers use to tell a story, comes in three main categories:
1. First person (the story is told from the perspective of I or We):
I grabbed Marcia's arm. "What was that about my wallpaper?"
2. Second person (the story is told from the perspective of You), generally in present tense:
You grab Marcia's arm and demand she repeat the crack she made about your wallpaper.
3. Third person (the story is told from the perspective of He, She, It or Them):
John grabbed Marcia's arm. "What's wrong with my wallpaper?"
Some authors use first or third POV only no matter what they write; others switch between first and third. Very few writers trifle with second person, the least-used and most difficult POV category, for various/obvious reasons. First, it's freaking hard to write in the past or present you form with sounding like a motivational seminar speaker's index cards: "After you make $5000.00 in your first week selling our Herbiagra Manhood Enhancement Product, you can start planning your retirement!"
I'm a switch-hitter when it comes to POV; I like first and third and will write whatever feels right for the story (and often I will change POV to suit the length of the story; the original short stories for the Darkyn novels were mainly written in first person, but all of the novel-length versions are in third.) I don't mess with second person in fiction, but I do employ it sometimes here on the blog.
For me second person seems far more intimate than first person, which is another reason I handle it like nitro. It's one thing to invite the reader into my fictional character's head with a first person perspective, and quite another to attempt to get into the reader's very real head by using second. You'd better know what you're talking about before you make that leap. While second person is just as effective when I'm serious as it is when I'm not, the form demands a certain degree of confidence and knowledge. Otherwise I'm not going to get into the reader's head, I'm going to be jumping over it, stomping on it, or kicking them in it.
When you consider which POV to use for your fiction, first look at the demands of the genre that best fits your story. Traditional romances are almost always told in third person; P.I. crime fiction stories are usually presented in first. SF/F waffles depending on what the current trends are (all the urban fantasy I've read lately has been written in first person, while all the traditional fantasy is still in third.) This is not to say you have to write only in those POVs, just be aware that the more popular a POV is in any given genre, the harder it's going to be to sell an editor a story with a different perspective.
Also, don't fall for what the POV snobs say about the different forms. I keep reading this one about how beginning writers mostly use first person because it's easier. Please. I didn't write a novel in first person until I'd first written 28 in third person (and wouldn't you know it, the first book I wrote in first person is the first one I sold.) While I love using first person for short stories, I still think a novel-length story is way easier to write in third.
If you're not sure which POV to use for your story, try writing a scene from first person, and then write it again in third. One of them will feel or sound more right than the other. But if for some reason they don't, have someone else read both scenes and ask them which is more engaging.
Finally, don't be afraid to experiment. You may not have much practice writing in more than one of the POV categories, but trying out different forms increases your range, and may provide you with a better connection to your reader. And if you don't want that, you definitely need to work on your POV.
Men with Pens' article Fiction Writing -- What's Your Point of View?
Two Heads Aren't Always Better than One by Robert J. Sawyer
Over at The M Factor, Mary Morel has a good article on how POV affects communication, and also provides a link to a Customer Focus Calculator that can read your website or blog and give you percentages on how customer-focused/self-focused your text is.