I remember in my Shakespeare class my professor asking for ten volunteers to demonstrate iambic pentameter. Each of us were to say one syllable from the famous
Romeo and Juliet lines:
"But soft, what light through yonder window breaks,
't'is the East, and Juliet* is the sun."
(*For this to work properly, you must imagine "Juliet" pronounced as it was in the Renaissance: Jule-yet. Two syllables.)
If you do this correctly, dropping out every other syllable (starting with the second), you will get:
"Soft light yon win breaks
is East, Jul is sun."
Doing this, you can get the basic gist of what Shakespeare wrote for these two lines.
Don't believe me? Let's take another two from
Macbeth, this time in trochee pentameter:
"Double, double, toil and trouble,
Fire* burn and cauldron bubble."
(*Like "Juliet," "fire" has two syllables. Say it aloud. Count how many times your jaw drops/moves downward. Pronounced like fi-yer.)
Again, take every other syllable out but this time, start with the first syllable:
"Doub- doub- toil troub-
Fi- burn cauld- bub."
Again, we get the basic outline of the lines. The point of the stressed syllable (in these examples) is that the word cannot be understood without it. For example, if we only do the lines from the
Romeo and Juliet example with the syllables we dropped out:
"But what through yon win
't the and -iet the"
The lines don't make sense now, right?
Let's try it again with the second example:
"-ble -ble and -ble
-re and -ron -ble."
Lot of "-ble" there!
Hopefully, this will make some sense. This is only for iambic/trochee pentameter, but I imagine that once you get the unstressed/stressed pattern down for other types, that would help. Simply start dropping syllables for the unstressed and keep the stressed in. Mark where in the line(s) the stresses are, and that will help you find the pattern. You can find a list of patterns
here.