Keeping control

Whatever your purpose for writing in English you must consider the language.

in an exam you have limited time and must produce good English quickly
If you are writing a report etc.. then you have to communicate something to your audience and it has to be accurate for them to understand

If you have planned well then your essay/report should almost write itself!

you know how many sentences to produce
you know the content of them
you should have a bank of 'formulae' at your fingertips to use
you should have a range of linkers to join everything together

Put all of this together and the only other thing you need is some good vocabulary and structure

this should be a fairly limited amount of language to add and therefore it should be possible to control the accuracy.

Pit falls

spelling - nothing is more irritating for a reader - make sure you have a list of personal 'spelling bugs' and check these words as you use them

grammar errors ditto - if you know you always miss the 3rd person 's' then be on the lookout for it as you go along

keep track of your subject and its attendant pronouns. If you're using lots of he/she/it maybe you've lost the subject and need to mention it again. If you're not sure then the reader will be even less so

long sentences - if your sentence goes over 2/3 lines check it to see if you've got lost in the grammar - a common fault (watch especially sentences beginning with .....ing

TRANSLATION - DON'T!! - translating is a high level skill which needs lots of training; unless you have had this DON'T TRANSLATE - it rarely works. If you don't know how to express it in English then try a different sentence or change the idea (less easy in reports etc for work - here, maybe using a noun instead of the verb, or making 2 shorter sentences would be clearer)