Anyone knows some efficient ways to imporve spoken English?

Usually I can use English to express myself and make people understand me without thinking, which should be a good thing. However, there are always some little mistakes in my talks. For example, I sometimes forget to add "s" after a verb which follows "he" or "she". Such mistakes, though would not lead a misunderstanding, are still problems that cannot be ignored.

So, Does anyone have some tips for me?