Determine the stressed syllables. When a syllable is emphasized in a line of poetry as it is read or spoken out loud, it is referred to as a stressed syllable. The word "stress" in this context describes the emphasis given to a certain syllable in a line.
Determine the unstressed syllables. The syllable that is not emphasized when read out loud is called "unstressed."
Take the word "danger" for example. Separate it into syllables and it looks like dan / ger. When you read it, the first syllable "dan" is emphasized, while the second syllable "ger" is not. Therefore "dan" is identified as a stressed syllable, while "ger" is categorized as unstressed.
Take a line from a poem as an example. The first line of Shakespeare's "Sonnet 18" contains a set amount of ten syllables. The first syllable is unstressed while the second is stressed, the third syllable is unstressed and the fourth reads as stressed. This goes on until the reader gets to the tenth syllable in the line:
Shall - I / com - PARE / thee - TO / a - SUM / mer's - DAY
Read the line to yourself. The unstressed syllables are in lower case, while the stressed syllables in upper case. Notice that as you pronounce each syllable, every syllable written in capital letters is emphasized. Try identifying the stressed syllables contained in the next line of the famous sonnet: "Thou art more lovely and more temperate"