I'm going into 3rd year and i'm thinking of postponing my Step 1 till either December break or after 3rd year is this a problem or can i do this? Also do i need do pass all 3steps to do residency in the US?

Step 1 doesn't cover clinical subjects, only the basic sciences. Take step 1 while everything is still fresh, then start your clinicals. People usually have Step 1 and Step 2 passed when the apply for their residency. During their residency they usually take Step 3, but I heard some hospitals and some people take all Steps and apply for residency.

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I procrastinate....

You need to take Steps 1 and 2 to apply to most residency programs, some will require Step 3. Take them as soon as you're ready, also to boost your chances of getting in (and get respect, money and lots of hot girls) you should do an elective in America. National Institute of Health is a great place for doing your elective. Also, a publication or two won't hurt.