I am not a SEO guy so not sure how relevant my question is.
We have to shift our web-site to a new domain due to some unavoidable circumstances but since the portal is up and running there from 2009 so have got a good index at various search engines and we are getting good page hits on daily basis.

loosing the search hits,index are our big concern and we are not sure how best we can handle this.

my question from the community is , what all can be done to preserve as much as possible while shifting to new domain name.