I've been a student from india till May 2011 and during this period I've been doing an internship. Then in June, 2011 I got my green card and started working for a company. I've received both form 1042-S(from the internship) and form W2 (from the job). I've been single trhoughout the year.
1. Am I considered a resident alien or dual status alien for tax purposes?
2. If considered dual status alien,
a) Can I elect to be treated as resident for tax purposes so that I will qualify for the Lifetime Learning Credit?
b) Can I still claim the standard deduction that I am eligible by the tax treaty for Indian students?
c) If yes to 2.b. how should I report this eligiblity in form 1040?
3. If considered resident alien or if answer to 2.a. Is yes,
a) How should I report both W2 and 1042-S in form 1040?

In pub 519 read "dual status aliens" on page 8 and read chapter 6 as well. Also read the example for Sam given at the end in pub 519. That will give you some clues.

Thank you nigam2012, for your quick response. The article and the Sam example answered most of my questions, but still I didn't get an answer to to be. According to the India Tax Treaty, I was eligible for the standard deduction when I was a student (non-resident). Can I claim the same when filing as a dual status alien?

You should see chapter 6 pub 519 4th para under "Income Subject to Tax"
See Chapter 9 page 57 under "Students Apprentices and Trainees" and Page 58 under "Students, Apprentices, Trainees ...who became" . Also read "Saving Clause" there. That should answer your questions.

You are dual status. You can not file as resident for whole year. Since you are F1/OPT income, you can claim tax treaty deduction as itemized deduction. You will also file Form 8843.

Thank you MukatA. That helped. As I understand I can claim the Standard Deduction of $5800 as an itemized deduction in form 1040NR which I will add as an attachment to my Dual Status 1040. Am I correct?

Yes