How to learn English writing effectively ?

The easiest way to learn writing English is reading. The more you read, the more you learn to write perfectly.

I can't put it any better than Anayat!

http://www.etutorialblog.com/to-write-articles-for-money/

Read this and after you can improve your english writing.

Exercise and keep writing what you like so as train yourself

Every grade has diffcult way for begginner , intermediate , pre-intermediate 

for begginners we can use with them  postcard to teach writting and after give them example about post card we asked from them to write postcard for any friend 

for pre-intermediate we can teach them how to write email interview and asked from them to write email to friend and asked for them to work in group 

for intermediate we teach them how to write report and asked them to write report about any thing