Writing is made up of words. Effective writing requires having a good stock of vocabulary, as well as selecting the most suitable words and phrases to express the intended ideas.
Remember, words are neither effective nor ineffective; they just impart different meanings to the sentences in which they are used. It is the writer's effective use of words and phrases that makes sentences effective or ineffective.
The English language is made up of nearly a million words and phrases. A writer, especially one whose English is not his or her first language, may face two major problems in writing: not knowing "enough" words; and not knowing how to choose the "right" words.
Right / Rightly
Right: immediately; rightly: justly, correctly.
e.g. Don't wait! Do it right now!
e.g. You will get your money right away.
e.g. I rightly canceled the trip: a storm was coming
e.g. We refused the offer, and rightly so because it was a bad deal.
Mediate / Meditate
Mediate: act as a peacemaker; meditate: think deeply.
e.g. The Secretary of State is trying to mediate between the two warring nations.
e.g. He meditated revenge after he was insulted by his coworkers.