Write in iambic pentameter -- follow unstressed syllables with stressed syllables. Iamb refers to one "foot" of unstressed and stressed syllables, and pentameter refers to the five feet in each line made up of 10 words.
Sum up the main point of the sonnet in the final couplet. For instance, in the Shakespearean sonnet XVIII, the couplet addresses the young man's beauty and brilliance stated previously in the sonnet as:
"So long as men can breath or eyes can see
So long lives this and this gives life to thee."
Ensure that the couplet uses a different rhyme pattern from the rest of the sonnet. The Shakespearean sonnet is identified by the following scheme of ABABCDCDEFEFGG. The final couple "GG" uses different rhyming words than the rest of the poem.