When you write something, you get very close to it. It is nearly impossible to distance yourself from it straight away to edit properly.

The longer you can leave a draft before editing, the better. Half an hour to two days is enough of a break to edit well. When you do edit, read your work out loud. You'll catch more problems and get a better feel for how everything flows.

It is more likely you've written too much than too little.
The rule for most writers is, "If in doubt, cut it." If a word, sentence, or paragraph isn't necessary, delete it. It will clarify what you're trying to say.

The beginning of anything you write is the most important part. If you don't catch someone's attention at the start, you won't hold it later.

You should spend a disproportionate amount of time working on the first few sentences, paragraphs, or pages.

The structure is what your writing hangs on. 

• A topic sentence that is followed by supporting paragraphs and a conclusion work best.
• Break up a series of paragraphs into concise points and, where necessary, insert subheads.
• For longer pieces, the structure will need a lot of work. Narratives need to flow, and arguments need to build. 

• A recommended how-to guide on writing good, clear English is “The Elements of Style” by William Strunk Jr. and E.B. White.

• “Politics and the English Language” by George Orwell is also worth studying to avoid “ugly and inaccurate” writing.
• A writing assistant like Grammarly can flag common writing, spelling, and grammatical errors.
• A good thesaurus is also essential for finding just the right word.
• A second pair of eyes. Ask relatives and friends to read over your work.