Presuming you're keeping the same domain and the changeover goes smoothly, there shouldn't be any affect on your site's rank at all.
I would suggest you upload site to new server a few days before hosting expires, change DNS, and wait for change to take effect. After a couple of days to be sure DNS has propogated throughout system, take down original site and notify host you will not be renewing site. Shannon
hi , Changing your hosing company is not a problem for a search engines.it only consider your site load time ..if your site loads slow means you may slip to next rank..
Hi there will be no affect on your rankings by changing the host, just make sure that the migration process is done properly with minimum downtime.
Changing the web hosting service or updating it, wont affect the ranking, if it is done before the expiry of the service. If you do it after the expiry, the ranking would go down and your site may be out of the top 100 or even top 300 ranking. This happens because when Google Bot crawls at that time, it will get only the host site like hostmoster.com or godaddy.com. The result will show that there is no such site and Google will consider that as your site and give ranking on that basis. That is why it always recommended to change the host before the expiry.
when moving site from one server to another, or one host to another for a smooth move, make sure to clean up your sites first, because there are usually a lot of junk which could cause problem in move, which should be cleaned for a smooth move.