Read more English articles, story books and English dailies. I'm not promoting The Star here but it's definitely a good source for you to learn or to improve your English.
I'm not saying I've a good command of English but definitely I like this language very much, thus I think first you need to sow your interest into it. This will help you a lot in your later days learning.
As you said you are weak in the usage of proper grammar, I think the best way is you keep reading and later come out with an essay every week if possible and request for help from the friends with better English to help you to point out your grammartical errors. It is proven scientifically that humans tend to learn better from the mistakes that made earlier.
Okay, as for the presentation part, I've no reason for not agreeing with edwuave. As a former choral speaker of my school which is one of the best teams in Malaysia, I think my teachers definitely have the sufficient experience to guide us the right way. They said we need to have countless practices in front of the mirror if we want to enhance our self-esteem to perform well in front of the audience, better pronounciation as in speak it aloud when you read a word and lastly it can improve your flexibility of facial expression. So, I think you might can use this way to improve your presentation skill.

My advice is to get your English brushed up as soon as possible before you graduate from your studies because it is important in your working life. I am not a what so ever pro in English but I do hope my suggested ways help you in a way.

If you were addrssing to me, sorry for the typo
Though I pronounce is at pronunciation
Quite funny, the verb is spelled as pronounce, but the noun is pronunciation.

To improve English, I think these tips do work (at least for me), you may take them as reference:

1. It is crucial to love the language. Yes, I really love English, ever since I was young.
   
   
2. Don't feel embarrassed to communicate in English. If others tend to correct your mistakes, take it as guidance and make sure do not repeat the same mistakes next time.
   
   
3. Do some reading. As for me, I'm not a bookworm. Sadly. Nevertheless, I read newspapers, online articles everyday and I'm a subscriber for Reader's Digest. RD is a very interesting magazine, I would recommend this to all.
   
   
4. To improve my vocabulary, I actually forced myself to read dictionary during my schooling days and of course I can't remember every single word that I read, I do not have superior memory.
   
   
5. Play words based games. I'm addicted to Facebook's Word Challenge.
   
   
6. To enhance your confidence in speaking English in the public, you can try practising talking to the mirror. Make sure your body language is good too. As for pronunciation, I installed a free software - Wordweb on my computer, it has the pronunciation feature. It is actually an English PC dictionary. You can get it for free here.
   
   
7. Try to write a blog, in English obviously. It is optional though. But blogging does help my language.

These are the methods on how I improve my English throughout these years. Of course, learning is a lifelong process. I'm also a learner and hope to learn from others too.

This post has been edited by fruitie: Dec 14 2008, 11:37 PM