Dated
When replying to a letter, do not say "Thank you for your letter dated on …..". The correct expression is "Thank you for your letter dated …" or "Thank you for your letter of ….". We should not say dated on.
Discuss
It is not grammatically correct to say "I want to discuss about …". The word discuss means "to talk about", so if you saydiscuss about, you are really saying talk about about. Same when you use the word mention. Cut out the about!
For example:
Mary mentioned that her report was overdue.
I want to discuss the agenda for next week's meeting.
In the workshop we discussed the new rules for good writing.
Due to the fact that
This is a wordy expression and can simply be replaced by As or Since or Because.
Enclosed herewith please find
The only word we really need in this cliché is Enclosed. It's so redundant to use herewith – if it's not herewith, where the heck is it? Please find implies it's like a game asking the reader to find something that's hidden. For 21st Century writing, throw out all the unnecessary wording.
Equipment
The word equipment is an uncountable noun and it should never end with an 's'. For example: We need some extraequipment for our new offices. All the new equipment has arrived. (use a singular verb) This equipment – the LCD, OHP and DVD – is needed in the Training Room.
Similar mistakes are made with words like luggage, baggage, furniture, information, clarification.
Everyday/Every day
Everyday is an adverb. Every day are adjective and noun.
For example:
Making your bed is an everyday chore.
I get the bus to work every day.
Having to write e-mails every day is an everyday task.