Write about a subject that captures the essence of the Goth culture. Vampire themes mixed with romance are popular, as are poems about castles, hidden lands and worlds beyond the one we live in. Gothic poems can also contain supernatural subject matter. Ghosts and hauntings can serve as the basis for a good Goth poem.
Write with words that step outside the boundaries. Keep a good thesaurus on hand. Look for words that aren't traditionally used and have a beautiful, almost trance-like flow. Ephemeral is a good word, and one that could easily be used in a Gothic poem. Choosing the right words can help give your dark subject matter an earthy, beautiful quality.
Develop setting and mood. These two components are essential to Gothic poetry. A castle set on a hillside, surrounded by fog, should be described in such a way that readers feel the setting and sense the trepidation of approaching. Here's an example:
The gray walls stand high;
Its black mouth
Waiting to swallow those who
Dare approach.
Using metaphors (one thing that stands for another) can help develop mood and setting. The "black mouth" as the entrance in this stanza gives the castle a darker personality.
Express your emotions honestly. If the Gothic poem you're writing is about something you feel, something you fear, or some insight you have, don't be afraid to place your emotions honestly on paper. Gothic poets are brutally honest and sometimes even dismal. Worrying about what someone will think of your words will prevent you from writing in this form.