Here are some basic definitions of POV types.  I'll go into each in
greater depth later-- this is just so you can identify which you're
most likely to use in general, and which you're using primarily with
this story.
Most common viewpoint approaches:
First-person:  In first-person viewpoint-- "I" -- the narrator is also
a character in the story, usually the protagonist.  Think of a
"biopic", a film of someone's life, with his voice-over narration.
This is common in literary fiction, women's fiction, and detective
books, and is much harder than it looks!  The reader knows only what
the narrator tells (though the narrator can dismiss clues the reader
finds significant), so the action is restricted to the narrator's
Tips:  1) Give the narrator a reason to tell the story-- to set the
record straight, to pass on history to a grandchild.  Lying, shading
of facts, defensiveness, blindness, are all terrific, as long as you
can put in subtle markers that the narrator isn't completely reliable.
Read Edgar Allan Poe's short stories for great examples of the
unreliable narrator.
2) Remember that the narrator is also a character affected by the
events of the plot.  If something emotional is happening, the VPC must
react to it and not just narrate (unless emotional deadness is what
you want to convey).
3) Since the reader is limited to this character's perspective, make
it a good one.  Make the POV character either a fascinating person or a terrific
observer, not just a pedantic reporter of events.
Omniscient:  In classical omniscient, an outside narrator describes
the action and the feelings and thoughts of the characters as necessary.
This narrator is NOT a character, but more of a godlike presence, who
knows more about the events than any or all of the characters,
including the future. ("Little did they know that ahead lay their
greatest trial yet" is the classic omniscient line.)  Think of a
documentary, with a voice-over narration by, oh, Alistair Cooke at his
most urbane.
Tips: 1) The narrator is a filter between the characters and the reader.
Often there is an ironic narrative attitude that seems to say, "These
amusing mortals..." Classical omniscient works best wheo you want to
keep the reader at a distance.
2) This is considered old-fashioned nowadays, but is still used by
writers of humor like Lemony Snicket.
Light or limited omniscient:  Think of one of those old films where
occasionally text scrolls across the screen, explaining the backstory
or a character's background. The narrator in light omniscient is not
so obtrusive as in classical omniscient.  But the narrator still
reveals that extra knowledge, especially of the history and the hidden
motivations of characters, which they themselves might not know.
Light omniscient can also reveal the thoughts and feelings of
secondary characters and groups without losing focus. Editors often
prefer this to multiple viewpoint or headhopping.

The Harry Potter stories are told in a "light omniscient" point of view for the most part, with Harry as the main but not only POV character, and a clear "authorial persona" in the descriptions of setting and character.
Tips:  1) This is still distancing, but there's not as much intrusion
from the narrator.  It works best in plot-driven books, where much of
the action takes place away from the protagonists, or in books with
ensemble casts without a single protagonist.
2) Remember to have some purpose for each "dip" into a character's
thoughts or feelings.  You might identify a couple major VPCs who
observe much of the action.
Multiple viewpoint:  Think of a disaster film like Airport or Jurassic
which follows the activities of many characters. Multiple
viewpoint has no narrator or authorial perspective, but dips into the
minds and hearts of characters as needed.  It is distinguished from
headhopping because the shifts in POV have some purpose, and the depth
of each viewpoint is controlled.  (For example, you might want to
reveal the secret romantic dreams of the heroine, but only the ewents
witnessed by the minor character of the maid.)  Editors usually say
they don't mind multiple viewpoint "as long as it's done well."
That's the hard part!
Tips:  1) Don't shift unless you know why you do it!
2) Beware of "stray viewpoints", especially of walk-on characters who
will never be seen again.  Only use the viewpoints of those characters
who have something of value to impart to the reader.
3) Signal shifts with some subtle indication that we're now in a new
head. An "action tag" can work: "Pensively John picked up the letter
and wondered why Julie didn't trust him."  Or use a "head" word like
"thought" or "mused".  "She had a lot of nerve, John thought, to say
she couldn't trust him!"
4) Never shift within a paragraph... except in extreme circumstances,
as when you hopskotch through a crowd picking up reactions.
Headhopping:  Headhopping, like bedhopping, is promiscuity: too much
iotimacy with too many people.  Think of live news footage of a riot--
without a reporter! It lacks the control of other viewpoint approaches,
and shifts from one vp to another without any discernible reason.
This trivializes the significance of being privy to the thoughts and
feelings of the important characters, and confuses the reader, who
expects that knowing the history and inner secrets of a character
signifies that person's essentiality to the plot.  Editors hate this
and see this approach as the mark of an amateur.
Tips:  1) To identify headhopping, print out a scene and, using a
marker, highlight each shift in viewpoint.  If you can't state a
purpose, change back to the previous vp.
2) If you're not sure what constitutes a shift, choose the character
you want as the major viewpoint character.  Change that person's name
and pronoun (he or she) to I, as if this were a first-person
narrative, and then read it out loud.  You've shifted whenever you get
something impossible like "Silently, Kate wished she could tell me
that my mother was actually my sister, but she knew that I would never
believe it."
3) Be especially wary of using the viewpoints of minor characters.  Do
we really need to know that the maid thinks it might rain?  Only use
this when the information is essential and there's no other way to
impart it.
Single POV:  Think of tightly focused films which follow one character
through an adventure and show only what he experiences.  (Hitchcock
did this in many of his greatest films-- Rear Window comes to mind.) This limits the viewpoint to one per scene, almost always those of major characters.  The reader
experiences only what the viewpoint character experiences, but if you
do it cleverly, you can leave room for the reader to interpret the
events differently from the character.  This viewpoint approach
decreases the distance between the reader and the character, and makes
the reader more of a participant (identifying with the character) than
an observer of all the characters.  It is the preferred viewpoint
approach in romance these days, and is worth mastering for the depth
of characterization that results.  It is much more flexible than you'd
think.  Variations include starting a scene with an omniscient "pan
shot" and narrowing to a single viewpoint after the stage is set;
"entering" a scene on one viewpoint and halfway through shifting to
the other for the "exit"; and deep-immersion (see below).
Tips:  1) Use the POV character's perception of others' body language, tone of
voice, facial expsession, to show what they're thinking, instead of
shifting to the other viewpoint.  The POVC might not interpret these
signals in the right way, but the reader will!
2) If you shift point of view in the middle or at the end of a scene,
skip a couple lines to indicate the change, and use "head words" to
identify the new viewpoint.
3) This viewpoint choice is effective both in deeply emotional books
like romances, and in mysteries, where the reader oeeds to keep track
of who knows what when.  In mysteries especially, the reader probably
should not have access to any clues the sleuth hasn't discovered,
which means very tight control of the information flow!
Deep-immersion:  Deep-immersion viewpoint is single viewpoint with the
action narrated (in third-person) by the POVC.  That is, within
reasonable limits, the terminology used, the phrasing, the thoughts
expressed, the perspective, of the narration should be that of the
POV character.  This is the most intense and intimate viewpoint approach, more
so, in fact, than first-person.  Why?  Because an effective
first-person narrator can and probably will lie.  In deep-immersion
third-person, the reader can assume that what's reported is the truth,
at least as far as the POV character knows.  Think of videos where the camera is
mounted on the helmet of the man skiing down the mountain.
Tips: 1) This is the ultimate in "show, don't tell". In
deep-immersion, the POV character's perspective is all the reader gets.
This means if the POVC wouldn't think it or notice it, it doesn't get said.
So much for "he passed his hand through his lushly wavy dark hair"--
he probably wouldn't think of his hair that way.  Try substituting "I"
for "he" to see if it works, and also act out the action.
2) Think about how this POVC would perceive the world, and narrate it
that way.  A musician will hear more than she sees, so make her
viewpoint audial.  A problem-solving sort will always be looking for
things to fix.   Don't overdo this, but this technique will truly
individualize your POVc's "voice".
3) The longer you can stay in one viewpoint, the more effective this
is.  Moving from one narrative voice to another every couple pages can
be jarring to the reader.
4) In historical novels, try not to use words in the narrative that obviously weren't in use during the
period. Be careful of obvious anachronisms, like, "Julius Caesar focused his laser-like eyes on Brutus."


I think your primary POV approach is probably chosen unconsciously. You probably are naturally a single-POV writer or a multiple-POV writer or whatever. Or sometimes the story dictates what sort of POV approach you will use. So there are no rules really. Just commit to your approach and do it as well as you can-- like in first-person POV, you might be sure to make the POV character's voice really apparent, and in multiple-POV, you might be careful to clearly identify a shift to a new POV character, so that the reader is never confused.

I'll post more about POV when I get more time. Here are a couple other articles that might be useful: Overview. First-person POV. And I have a book out from Writer's Digest that goes into this more deeply.