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. You don't
want to capture audio form a distance. 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. 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.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.

?url? http://www.rodemic.com/?pagename=Home?/url?
Rode is an inexpensive mic - they are okay for recording instruments but
their shotgun mic?s aren?t very versatile.

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?

Then 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.

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