The detailed list of number of vacancies, is usually available on the dghs website (its link is usually available 2 - 3 days before the start of the counseling at AIIMS website ( http://www.aiims.ac.in/ or http://www.aiims.edu/ )
After the counseling begins, DAILY, at the end of the day (i.e. usually by 6.00p.m.) the current status of available vacancies is updated on the dghs website. (So, you may go to Delhi just one or two days in advance. And keep a track of the vacancies via internet.)
The appointment letters are available the same day (usually), so that you can plan to return to your place by the train after 6.00 p.m.
(The above information is based on responses of candidates who have attended previous years counseling. We do not guarantee the accuracy of the information. Please verify it from reliable resources. Any information that you think helpful may be submitted by the feedback form.)