Do not overuse similes, saying something is like something else. Poetry is usually improved by metaphor. The yellow sun is like an egg yolk can become the sun is yellow as an egg yolk or the sun is egg yolk yellow or simply the sun is an egg yolk or just the egg yolk sun. Then you can start thinking about albumen clouds.
Beware the use of weak verb endings. A phrase sounds more dynamic, direct and active without them. The dog is barking is made more immediate when the dog barks.
Doubly beware the use of adverbs and adjectives, which lack precision and again weaken your phrases. Instead of he runs quickly say he hurries or he hastens. Otherwise, devise a metaphor involving a zephyr or some such fast moving thing, unless it clutters the scene.
Avoid repetition. You may have favourite turns of phrase and images, but should employ each one only once in a manuscript – unless making a deliberate cross-reference or echo.
Be specific. For example, when you say bird, you may picture a starling while the reader sees a sparrow. This affects the accuracy and effectiveness of your images. It is like using a generic piece of clip art rather than an actual photograph. Remember, names have power. A dove and a hawk are both birds, but symbolize contradictory attributes.
In a similar way, when you say something, you are avoiding the challenge of articulating more exactly what that thing may be.
It is so easy to fall back on well worn phrases and sayings, especially when they convey exactly what you want to express. But poetry is about communicating your unique point of view, your personal thoughts and experiences. Place yourself in the situation. What do you honestly think and feel? What does each of your 5 senses tell you? Remove the filters through which you normally perceive the world and admit the truth, no matter how painful. Only resort to cliché in the interest of bathos or irony. Show, don’t tell.
Be careful about asking the reader questions, unless you answer them. It can sound badgering and the reader may feel backed into a corner and demand How the **** do I know? You tell me! Even a rhetorical question can be problematic, as it assumes the reader sees things the same way you do.
Exclamation marks are, of course, beyond the pale.
The first draft of a poem is often a journey into mystery and you don’t know where it’s going until you arrive at the end. Looking back over your path, you may see all sorts of twists and turns and diversions and dead ends you mistakenly took on the way. For the benefit of fellow travellers who follow after, it is probably best to simplify your route. This is also known as kill your darlings.