The English language abounds with homophones, words which share the same sounds, but have different meanings and, especially, spellings. There are also near homophones. These can be confusing to writer and reader alike. Most of the time the context tells the reader which word is intended, but sometimes it may mislead the reader. Therefore, it is important to properly spell the word you are using to clarify your meaning. The wrong choice among homophonic spellings may not only confuse your readers, it can make them stumble in reading your material. And it can make a poor impression when a good impression counts. Examples of this are resumes, cover letters and reports.
So how do we keep homophones straight? We may memorize many sets of homophones. But many of us have trouble just remembering what amounts to another list. I suggest using mnemonics. A mnemonic is a device which aids memory. What I am suggesting is mnemonic sentences or phrases which use the homophones in a set together in the same context. Just bringing them together reminds us that there are different spellings of same-sounding words which carry different meanings. I will give a few examples. You may create others to assist you in your writing.
Homophones: there, their, they're
They're over there with their luggage.
Near Homophones: weather, whether
I wonder whether the weather will be rainy or sunny.
Homophones: to, too, two
You have to mail two letters to Mr. Jones too.
Homophones: accept, except
They will accept all of these except that one.
Homophones: affect, effect, effect
This decision will affect every one of us adversely. The effect is unacceptable. Please do not effect this policy.
Homophones can be on the humorous side:
Tutu taught English as a Second Language (ESL) to immigrants. He was teaching Phan and Thu [pronounced "TOO"]. Phan learned fast, and soon moved from Level One to Level Two. One day Tutu's ESL supervisor came to him and asked, "Phan is almost through Level Two. When will we get Thu to Two too, Tutu?"
(This was posted on my tutoring blog on WyzAnt: http://www.wyzant.com/Blogs/Wesley_G_V/Mnemonic_Sentences_Help_Distinguish_Homophones/ViewBlogPost.aspx?id=276 )