An anonymous reader asks, "How do you get good at 'listening' for iambic pentameters?"

Poetry, like music, has rhythm. In music, the rhythm is established using a few different intstruments. In a band, the drummer and the bass guitarist are the primary rhythm-holders. Those deep, bassy sounds like the guitar and the kick (bass) drum set our subwoofers to vibrating, and mimic our own heart rhythms.  In some music, the rhythm is prominently defined by the kick drum and the snare drum. A GEICO ad from awhile back made this point with a pig singing "Boots and pants and boots and pants and..."

The words "boots" and "pants" represent the kick drum*, and the word "and" represents the snare. The kick drum provides the primary driving beat, and the snare represents what we call the "off-beat".

So the pig is actually giving you the beat of a song.

You can feel the rhythm of that if you repeat it over and over, and if you do it just right, it's almost indistinguishable from a techno band.

The rhythm of a poem (in poetry, we call it the "meter" of the poem) can be understood in terms of kick drums and snares, which means it can also be understood in terms of phrases like "boots-and-pants-and". In poetry, we have stressed syllables and unstressed syllables. Stressed syllables correspond to the driving "kick" beat, and the unstressed syllables correspond to the off-beat of the snare. So what does iambic pentameter look like?

and-BOOTS-and-PANTS-and-BOOTS-and-PANTS-and-BOOTS.

Notice that we start with the snare, or the off-beat, and we end with the kick. Also notice that we have 5 kick beats. This is why it's called penta-meter; "penta" is five and "meter" is rhythm, so pentameter is a five-rhythm.

The nice thing about having five kicks in a line is that you've got five fingers on one hand, so while you are saying "and boots and pants..." each time you say either "boots" or "pants" you can tap a finger on the table, and when you've tapped all five fingers, you've completed a line of the rhythm. So if you want to get good at listening for iambic pentameter, do this repeatedly. Say the "and-boots" pattern while tapping out the kick beat on your fingers. If you want, after you do the fifth finger, give a little pause, and then start all over again:

and-BOOTS-and-PANTS-and-BOOTS-and-PANTS-and-BOOTS [pause] and-BOOTS-and-PANTS-and-BOOTS-and-PANTS-and-BOOTS [pause] etc.

After awhile, that rhythm will get ingrained in you, and you'll be doing it without even thinking about it. Now let's take a look at something that's written in iambic pentameter:

The quality of mercy is not strain'd,
It droppeth as the gentle rain from heav'n
Upon the place beneath: it is twice blest;
It blesseth him that gives and him that takes. (Shakespeare, The Merchant of Venice)

If you've got that "boots-and-pants" thing going through your mind, it'll be easier to see that this is iambic pentameter:

the QUAL i TY of MER cy IS not STRAIN'D
it DROPP eth AS the GEN tle RAIN from HEAV'N
u PON the PLACE be NEATH: it IS twice BLEST;
it BLESS eth HIM that GIVES and HIM that TAKES.

Can you feel the rhythm of it?

Important Disclaimers

1. Thinking "and-boots-and-pants" may be a great way to recognize and understand the rhythm of poetry, but it is NOT a good way to read poetry; nobody wants to hear Shakespeare sounding like techno music**. Instead, you should use boots-and-pants to help you recognize where the beats are, but then once you've understood which syllables get the stress, you're going to read this in your normal reading voice, without giving unnecessary extra accent to any syllables.
2. Also, even though when you practiced the rhythm, you left a pause between lines, you won't necessarily do that when reading a poem. Focus on the meaning of the lines; if a line does not complete a thought, you're not going to pause at the end of it. And if a thought is completed within a line, you're going to pause there. Remember that meaning is most important, and rhythm serves the poem, not the other way around! So with this in mind, the Shakespeare piece would be read like this:

The quality of mercy is not strain'd, [pause]
It droppeth as the gentle rain from heav'n upon the place beneath; [pause]
It is twice blest; [pause]
It blesseth him that gives and him that takes.

Other Meters

The "boots-and-pants" idea can be used to recognize other meters as well. For example, if you want to get the feel for anapestic tetrameter, you should start thinking:

and-the-BOOTS-and-the-PANTS-and-the-BOOTS-and-the-PANTS.

Notice that we've added the word "the" after the word "and" each time. This gives the meter a "triplet" feel. Also note that we only hit four driving beats in a line instead of five. So if you're counting this on your fingers, leave out your thumb.

You can see this rhythm in the well known Christmas poem "Twas the Night Before Christmas":

twas the NIGHT be fore CHRIST mas and ALL through the HOUSE
not a CREA ture was STIRR ing not E ven a MOUSE

* Technically, "boo" and "pan" represent the kick, and the "ts" represents the hi-hat. Thus, we really break it down like this: BOO-ts-and-PAN-ts-and.

** Well, okay, maybe "techno-shakespeare" should be a thing. But I'm not sure your poetry teacher will appreciate it!