To find the rhyme scheme of a poem, look at the last word in each line of the poem for a few lines, as some rhyme schemes are very basic and some span eight or ten lines of the poem. Rhymes at the end of lines are called “end rhymes” and are described using letters to indicate distinct rhymes. If the first and second lines have the same rhyme, and the third and fourth lines have the same rhyme, the poem has an AABB rhyme scheme. Consider "Humpty Dumpty":
Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall...
Rhyme schemes are described using letters to indicate distinct rhymes. If the next two lines have a different rhyme, the rhyme scheme is called ABABCDCD.
While rhyming is fairly straightforward to measure -- just look for the same sounds at the end of the lines -- meter is more complex. Meter refers to the rhythm of a poem. This isn’t the same as rhyme, even though the words have the same root. Rhythm refers to the sound of each line of poetry, not just the last sound, and meter is a way of counting or identifying the system of rhythm used. Poems without meter or rhyme are called “free verse”; other poetic forms adhere to meter patterns almost religiously.
The measure for rhythm or meter in a poem is called “scansion,” which refers to parts of each line called metric feet. A foot is a two- or three-syllable section of a line with a particular sound pattern. There are five basic forms for feet in poetry: iambs, trochees, anapests, dactyls and spondees. Each of these refers to a different syllable stress and count. Iambs are two-syllable sounds where a weak syllable is followed by a strong syllable; trochees are the reverse, a strong syllable followed by a weak one. Anapests are two weak syllables followed by one strong one; a dactyl is the reverse of an anapest, with two weak syllables following one strong syllable. Spondees are just two strong syllables.
Examples of Feet and Measuring
Look at the following line of poetry:
The time of year thou mayst in me behold...
There are ten syllables, and every other syllable (time, year, mayst, me, hold) is stronger than the one before. This line is made up of iambs; if there are five of them, you refer to this line as iambic (made of iambs) pentameter (five of the same meter).
Or consider the following:
Tell me not in mournful numbers
There are eight syllables here, with the stress on the first part of each pair, meaning this line is made of trochees. Since there are four sets of trochees, this is called trochaic tetrameter. Lines with three groups of sounds are called trimeters and lines with six syllable groups are called hexameters.