Even native English speakers -- me included -- struggle with grammar and word usage. This site provides an extensive list of common errors and explains their correct usage. The author, Paul Brians, is a professor in the Department of English at Washington State University.
Note: The above link takes you to an FAQ page. The link to the full list appears at the bottom of this document.
Here are a few examples.
“Dual” is an adjective describing the two-ness of something—dual carburetors, for instance. A “duel” is a formal battle intended to settle a dispute.Due to the fact that
Although “due to” is now a generally acceptable synonym for “because," "due to the fact that” is a clumsy and wordy substitute that should be avoided in formal writing. “Due to” is often misspelled “do to.”Oppress/Repress
Dictators commonly oppress their citizens and repress dissent, but these words don’t mean exactly the same thing. “Repress” just means "keep under control.” sometimes repression is a good thing: “During the job interview, repress the temptation to tell Mr. Brown that he has toilet paper stuck to his shoe.” Oppression is always bad, and implies serious persecution.