[inglor_cz]

At the risk of sounding smugly, just write. Perhaps ask someone to read your texts, but don't rely too much on random critics. Individual people have their own taste and pet peeves; what is unreadable for one may be enjoyable for others.

Writing is like hiking or skiing. While there are some important rules how not to kill yourself, you can only learn it by doing.

Also, read a lot, ESPECIALLY works by people who have a good command of your language (IDK if you are native English speaker; I am not). Writing style is a bit contagious. Don't worry if you occassionally sound like someone else, this kind of contagion is really unavoidable if you read a lot.

I would say that the optimal ratio of R:W time is about 5-6:1.