It is not too difficult to iron out little faults when writing poetry, and just a few small mistakes can easily be the difference between getting published or winning a poetry competition.
When writing the first draft of a poem you should, initially, focus on the poem itself, and not worry so much about the spelling, nor even the grammar and punctuation. The first draft should really be the core of the poem you are trying to write. Think of it almost as an 'ideas' poem. This will make things interesting, stimulating, and fun, rather than expecting too much, and beginning the poem looking for an immediate polished piece of work.
Stage two should see you study the poem more closely, and check every line. A bad line will normally stick out like a sore thumb. It may not scan very well, seem irrelevant to the poem, or it may be a lazy or forced rhyme - for example, a lazy rhyme such as rhyming the words 'kind' with 'time'. Often, a forced rhyme can upset a poem's scan, as a common mistake is to focus more on the rhyme rather than making sure that a poem does indeed scan. A forced rhyme could be something like 'sane' and 'aeroplane' - a two syllable difference.
With rhyming poetry, always check the amount of syllables in your work. Sometimes rhymed poetry will work well with uneven syllabic structures, but not always. Just remember also, that an equal syllabic structure doesn't necessarily mean that a poem will scan either. But there are no hard and fast rules, and you should always read through your poem several times - even at an early stage. Also, take a break and then come back to the poem, as you may notice mistakes you missed earlier.
For the third stage of writing your poem, you should begin to tidy your poem up, and check the spelling. If you are still having problems making your poem scan, then tweaking the punctuation may make a big difference, and check the grammar, too. This third stage should really just be a tidying up exercise.
Do not be too laborious in your approach if you're writing a short poem, as it may lose some of its spark. Always try and make writing poetry interesting. It's better to take as many breaks as you need, to keep your mind fresh, than to rush through things. Enjoy the whole process and your work will definitely benefit.