There are fourteen lines in a sonnet. Typically, these lines are divided into four groups. The first three groups of lines consist of four lines. The final group of lines consist of two lines. Usually, the groups center on the rhyme scheme of the sonnet.

Not all sonnets share the exact rhyme scheme. If you read William Shakespeare's sonnets, you'll find their rhyme scheme is different from those of Edmund Spencer. Conversely, if you read Edna St. Vincent Millay's sonnets, you might discover that she has the same rhyme scheme as Shakespeare but not as Spencer.

Some poets eschew rhyme altogether when they craft their sonnets. Better put, perhaps there is rhyme, but it's not so obvious. You might want to look at a poet like Wanda Coleman and see how she reconfigures and remakes the sonnet form.

As for the individual lines of each sonnet, most standard sonnets are written in iambic pentameter. They contain ten syllables.

The first line from Millay's "Sonnet I" has ten syllables:

Love, though for this you riddle me with dart ...

Even the first line of Coleman's "American Sonnet (35)" has ten syllables:

boooooooo. spooky ripplings of icy waves. this ...

If you continue to read more of Coleman's sonnets, you'll notice that each of her lines don't always contain ten syllables. If you're interested in how other poets have made their own mark on the sonnet, you might want to check out Nick Demske by Nick Demske or Nets by Jen Bervin.