The sonnet is a form that has been employed for about 800 years, give or take some lapses in popularity. It's an easy form to describe and possibly one of the best examples of form aiding the poet's capacity for expression. Simply put, there are very good reasons why it is such a popular form.
Specifically, we are going to write a Shakespearean sonnet. Or, rather, I am anyway and that's the type I'm going to describe here. If you feel drawn to write a Petrarchian sonnet or a free verse sonnet or any other kind of sonnet, don't let me stand in your way. The form was adapted into what became the Shakespearean sonnet to aid in English usage. As Stephen Fry puts it, in Italian, every other word ends in -ella or -ino. The Shakespearean gives more variety of rhyme.
So, here's how it is done. Fourteen lines sectioned like so: eight lines, then six lines. The rhyme scheme is abab, cdcd, efef, gg. Traditionally, the topics are love or philosophy, usually on one specific thought or subject within those topics. You make an observation or description in the first eight. In the latter six you reveal what you think of it and what conclusion you come to on the topic. Or, if you're like me, you just try to at least get it on that dart-board.
I must confess that I have a devil of a time with rhymed couplets, which is part of why I'm doing this exercise. If you're like me, form poetry is a difficult thing to begin with, but so often I have found that the difficult things are the things worth doing. I'm always afraid when I embark to write in rhymed couplets that I'm going to come out with a trite Hallmark card. I look to W.S. Gilbert and Shakespeare. I would encourage all of you to look at as many other sonnets as you can before starting this exercise (there are so many. Shakespeare and Petrarch obviously, Ted Berrigan, Lord Alfred Douglas, Donne, Milton, Spencer, Browning, Millay, e e cummings, and many many more.) First of all, it always helps to fill your brain with greatness because then greatness is what will be in your brain. Second, and more importantly, it also helps to see another writer having fun with the form.
As usual, I will go first.
Sonnetic Advice to Some Young Men
by Paul Mathers
You gentlemen who wish to assign roles
to gender, strict as algebraic forms,
remember the variety of souls
it takes to see the ship survive the storm.
If you should wish to find a love that's lasting
and you've a rigid list of traits you'd rather
you may as well just call up Central Casting.
To you what's inside one is like another.
For when you come to love another person,
The person is the thing you come to love.
So, make sure that that crush that you are nursing's
A person you could stand to keep abreast of.
Unless it's someone you view as a friend
you're doomed to have your love overextend.