That's a great question, Tejaswini! Worth an essay (or a book), but for now I'll just offer these points to keep in mind:

1. The best word choice is the one that comes closest to expressing what you're trying to communicate to the reader, whether that's an image, a feeling, a memory, or whatever. In other words, say what you mean, don't choose a different word just because it sounds more poetic.

2. All other things being equal, Anglo-Saxon or German-based words pack a stronger punch than words of French or Latin derivation.

3. If you choose your nouns and verbs well, you won't need many adjectives or adverbs. Use modifiers mainly to twist the meaning or surprise the reader, as in "killing me softly."

4. Read Carl Sandburg to learn the power of simple words. "I wish to God I never saw you, Mag."

5. Poetry is best appreciated when read aloud, so that you can feel the impact of the words upon your ears, and the way they feel in your mouth and throat. They need not always be smooth and languid, because sometimes one must, like Neruda, explain a few things.