If your grammar isn't too good, it's not too hard to solve.
First, in short term, read more grammar guides and do more practise(although it's sometimes quite boring,it helps).
Seconf, in mid term, try to write more essay and be corrected by your teacher. Lean from mistakes.
Thirdly, in long term, try to read some books or fictions that you are interested (for example movie-packed fictions), see how pasages are written, eg usually stories are told in past tense.
Enhance your english proefficiency needs your own effort. I'm not saying tutorial cources arent good, but they do not concentrate much on grammar and may not help you improve much.
2007-01-07 21:52:57 補充:
sorry,typing mistake, second