hello sir.. I have registered in all India counselling neet but not alloted any college in first round. what to do to participate in 2nd round?

If you haven't got any seat in First round of counselling you can surely go for the second round. After the declaration of first roound results, the second round starts after few days. You can directly participate in the second round of the counselling. For that you have to go for upgradation or you can go for upliftment. Th authorities will publish seat matrix of vacant seats and accoridng to that you can re arrange or re shuffle your choices if you wish to. And in second round if you are allotted to a college and if you wish to join you can lock your college. You can check out this link for further Information http://medicine.careers360.com/articles/neet-counselling-faqs