cburr, I wish you had taught me "call the dog" about twenty-five years ago! What a great teaching technique! Would have saved me--and my students--a lot of work.
One thing we did do, although I think "call the dog" is more effective, is "play the drum." We would read (chant) lines of poetry aloud for practice, and play the drum to find the rhythm of the strong beats. Their drums, of course, were their desk tops. They loved this activity, as you would expect. During quizzes, sometimes I would see a student very quietly tapping on the desk, so I guess it worked. But I still like "call the dog" better. That is no-fail.
The advice given in the previous posts is excellent. I just want to add that, many native speakers (including some English teachers themselves) have difficulty distinguishing between stressed and unstressed syllables. It may take a little time to get the hang of it, but if you follow the the excellent advice that was posted, you should do fine.
One trick that is often useful in teaching dyslexic children to read multi-syllabic words with stress on the right syllables is to "call the dog". I realize that this may work only if you have grown up in an English-speaking environment. However, if you call out a word as if you were calling a dog's name, you naturally put the stress in the right place. Con - sti - TU - tion is an example. I hope this is of some help.
Identifying the stressed and unstressed syllables in an English-language poem is for the most part a matter of following the pattern of the metrical feet. As parkerlee points out, "The Eagle" is iambic tetrameter. This means that there are four feet per line ("tetra" means "four"), and each foot contains an iamb (two syllables, first unstressed, second stressed). Knowing this pattern will help you to diagram the feet line by line.
To find stressed and unstressed syllables, you have to listen carefully to yourself as you read the verses, preferably aloud. Which syllables, not words, do you emphasize? For instance, consider a name. Say the name is Frankie. Do you pronounce it FRAN- kie or fran- KIE? Or look at another word like eagle; do you say EA-gle or ea-GLE? The goal is to read a line as normally as possible. Being a student that might not speak English regularly, this might be a challenge. However, when you listen to English being spoken, pause and ask where the stress in syllables are. For example, if you watch a news broadcast, like BBC or CNN, listen to how the news is being read by the broadcaster and pay attention to what is being stressed and what is unstressed. While I don't know other world news organizations in their native country, I know that in India, for example, watching NDTV or Headlines Today will help as they broadcast Indian news in English. This might help you in the realm of poetry, also. Here is a line from the poem that might illustrate this:
The WRIN|-kled SEA |be-NEATH |him CRAWLS = 4 stressed syllables.
AND LIKE a THUN-der-BOLT he falls.= 4 stressed syllables.
For a student not familiar with English, listening to how it is spoken will give you a better frame of reference as to pronunciation of terms and words. It will also allow you to understand where the stress in words falls and how this can be seen in poetry.
Listening to poetry with metered verse and music with lyrics (other than rap, which often accentuates the wrong syllable) would probably help. Only significant exposure to a language will help your ear "tune in" to correct stress, intonation and cadence.
You might enjoy reading two books by the famous orthophonist Alfred Tomatis. I read them in French so am not sure about their titles in English, but translated literally they are The Ear and Life and We Are All Born Polyglott.
In the poem "The Eagle" by Tennyson, each line is divided up into four meters, each with first an unstressed syllable, then a stressed one:
He clasps I the crag I with crookI ed hands;
Close to I the sun I in lone I ly lands,
Ringed with I the a I zure world, I he stands.
The wrin I kled sea I be neath I him crawls:
He watch I es from I his moun I tain walls, 5
And like I a thun I der bolt I he falls.
Here it's fairly easy since it's predictable - unstressed, stressed, unstressed, stressed, etc.... In official terms this is called iambic tetrameter.