Since nobody create this, i think is ok to make 1 to ask.

If i would like to resign, my resignation letter should be addressed to my supervisor, my GM or directly to HR?

If I need to serve for 3 months notice as stated in my employment agreement, then do I need to write in the letter that I will worked until what date?
If need to write the date, then how about if I or my new employer like to pay for the remaining 2 months notice, then should I stated in my letter as well so that the leaving date will be adjusted?

By right, the resignation letter is to be address to your immediate supervisor but then at the bottom to put CC to the human resource department. I have went through this a couple of times already, and have no problem with that.

I would like to add that your letter of appointment or contract should state the number of month/day/year that is required for notice to be effective.

Let Say at you job offer letter that u need to inform your current company for 3 months notice, then it's that mean on 3 months "WORKING DAYS" start couting from the date I issued the resignation letter?

I think that's looking at it wrongly... start counting based on non-working days too...

for example, today is 20 Mac 06, 3 months notice for resignation, then your last day is on 20 July 06

If you don't mind burning your bridges, just write "I Quit". Let HR calculate the notice period minus leave days.

I think the letter should be addressed to the pperson who hold the position who appointed you. less than 3 months notice might mean less than that 24 hrs. Look for "in lieu" condition in contract or agreement.

I think the step should be
1. have a personal meeting with direct manager/supervisor. Tell him you wanna resign. probably he will ask why. then u tell him got better offer bla bla bla or homesick and so on.... he usually will brain wash you, this is natural manager skill... NEVER disclose where you going.

2. Submit resign letter then CC HR like what phoenix mention. in the letter should have date as of today. then in the letter "as required by company policies, my last day reporting to work will be on <date after 3months of notice>. During this period, I will ensure transition run smoothly to my successor" you rearrage the words la... seems crappy abit. last line should thanks manager for the mentorship and guidance and oppurtunity given bla bla bla

3. wait and goyang kaki. always arrange and maintain good relationship with ur manager or collegue even though u hate them. you can always talk to your manager say this is what i have transition to who who who and what u going to teach next prior leaving. this to show u still loyal to the company. so next time u wanna come back still can.....

hope this help