Hi Everyone!
I found this article that you might be interested in. This is a list of the top 10 most common mistakes that people make. Yes, even native speakers!
The most common mistake that I have seen native speakers make is mixing up possessive and plural (number 7). The most common mistakes that I have seen a lot of English students make are numbers 5 and 10. How about you? Do you make any of these mistakes? Or do you always make one in particular?
http://finance.yahoo.com/news/top-10-grammar-mistakes-people-163200634.html
Have a great day! :)