What is the procedure and structure of JosAA counselling after Jee Main Ranks come out ? What are the tips (or tricks )that should be kept in mind ? How is JosAA different from JAC-Delhi in terms of procedure ?

Hello Yadvendra,the result of JEE Advanced are announced around 2nd week of June and after that the councilling of Joint seat allocation authority (JOSAA)  starts around 4th week of june, first of all there is choice filling by the candidate at the site of JOSAA after that seat is alloted to the candidate on the basis of choice, if you want you can lock that choice and accept that seat for admission,or you can go for further rounds to get better preference choice, after locking your choice time is given to the candidate for reporting to the reporting centres for document verification and seat acceptance and paying seat acceptance fee.There are first 7 rounds for NIT's, IIT'S, etc and then two special rounds for NIT's.
the point you should keep in mind is that you should fill your choices in preference order and do detailed research about the branch which you want to take, Don't accept the seat in starting round if you are not getting a good branch and college, wait till the 6th or 7th round to accept the seat.
And most Surely participate in Special round as the cutoff of special round comes quite low as many people's don't participate in special round and you will be benefited by that.