Just to clarify: Some people are confused about a "boom mic". The
"boom" is a piece of equipment - most often a pole of some kind
- that the microphone is attached to.

What you're looking for is a good shotgun mic. That in itself is a
generic term that means any long barreled mic. You want a good
condenser (externally powered) mic with a ?lobar? pick up pattern
to put on your boom pole. Lobar pick up means the mic focuses
its audio pick up to a narrow area. This is why you want to use a
boom pole to get the mic as close the the actor as possible - you?ll
get clean dialogue tracks with less ambient noise.

?URL? http://www.sennheiserusa.com/newsite/?/URL?
Sennheiser is the mic most used by professional sound recordists.
They are expensive and worth it. Check out the ME-66 and the
ME-67. The MKH60 is the best if you can afford it.

?url? http://www.audio-technica.com/?/url?
Audio-Technica is cheaper. Check out the AT835B. It?s a workable
mic, a little muddy and not as directional as it should be. The AT835ST
is a good mic for the price, but it, too, sounds a bit muddy - the
vocals don?t sound crisp enough for me.

?url? http://www.rodemic.com/microphones.php?/url?
Rode mics are quite good. Check the NTG (shotgun) series.

?url? http://www.azdencorp.com/?/url?
I?ve never used Azden mic?s. They?re inexpensive and I don?t hear
too many good things about them, but if that's all you can afford
it's MUCH better than using the camera mic.

A good mic is an investment. It will last longer than your camera - why
skimp? A great place to check prices and purchase is B&H Photo
?url? http://www.bhphotovideo.com/?/url?

The further away the mic is from the actors, the higher the volume
needs to be. The higher the volume, the more ?noise? you get. Your
goal is to have a very high signal to noise ratio - more signal (the
dialogue) less noise (the background). Even a very good, expensive
Sennheiser mounted on the camera will pick up a lot of background
ambiance because it?s far away from the actors.

So you need a boom pole. This can be as simple as a painters pole
with a microphone shock mount on it - or a 3 or 4 section, expandable
Carbon Fiber, Graphite Fiber or Aluminum boom pole. The lighter the
pole the better. Expandable is also very convenient. A pole that?s a
fixed six or eight feet (painters pole) can pose problems if you?re shooting
in a small space like a bathroom or small apartment or if the boom
operator needs to be twelve to fifteen feet away to be out the the lights.

A good Graphite, five section boom will be light, range from two feet
to nine feet and cost $500 or so. A pro boom-op will invest in a good
pole. No need to spend that kind of money if you?re making one or two
shorts a year.

Yes. You can play around with sound using Final Cut Express.

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The aim of an argument or discussion should not be victory, but progress.
Joseph Joubert, essayist (1754-1824)

Hey, that helped out a lot! Thank you so much for all of the information.