diplomatical letter

Recently, because of my job requirements, I have to write some diplomatical letters to my business partners. For example, invitations, applogy for meeting postpone and so on. Sometime I confuse if I wrote perlite enough or If English speakers do use such sentences as I used to use in those letters ( My English is not good enough) . How can I have better skill of writting diplomatical letters? Can somebody help me?

Forum: Common English Questions and Answers - Archived Posts
Posted: May 22, 3:11 AM [GMT 1]
Post Subject: [url="/English/Post/cmznc/Post.htm#227666"]Re: How to pronounce a 't' in American English[/url]
Post author: [url="/user/czbm/profile.htm"]CalifJim[/url]

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Allophones of /t/, continued.

Other symbols that will be used in a chart to follow:
V' stressed vowel a vowel relatively more stressed
syllable of the word
'V unstressed vowel a vowel relatively less stressed
syllable of the word
V any vowel any vowel, whether stressed or not
L syllabic L as in the final syllable of "little", "curdle"
(always unstressed)
N syllabic N as in the final syllable of "satin", "carton"
(always unstressed)
/ "or"
b# beginning of a word
e# end of a word
C consonant any (other) consonant
not mentioned in a list
(down the left side or
across the top of the chart)

To be continued.
CJ