How to prepare for USMLE?
Step 1 can be taken anytime after the second yr of MBBS.
Step 2 consists of 2 exams : CK and CS i.e. Clinical Knowledge and Clinical Skills respectively.
While step 1 and step 2 CK can be taken in India at the Prometric centres, step 2 CS is offered at 4 centres in the US only as it is a practical exam where simulated patients are given to you with different case scenarios.
Step 3 is the last step and can be taken either before or after applying for the match.
Apart from clearing these examinations with good scores, you must have certain activites which give you an edge over the others like Research, US clinical experience in the form of electives or observerships, voluntary work etc.
This is the basic overview of the USMLE. Feel free to ask any more queries and i will be more than happy to help.