Backup- you must take it now: You know the importance of it, just like having a good insurance package that can gives you support in danger! If you havent taken any backup yet just go for it now. Take the backup of anything that you think important for you and specially do not forget to take backup of your site database when your site depends on it.
While moving to any different web hosting service provider its advisable to take your backup manually after downloading all the files. Please follow ASCII or Binary transfer type while downloading. If the server logs are equally important for you its always better to take the backup to avoid difficulties on later.
Checking internal Links is a mandatory step that you need to follow. You have to check properly that there are no more any hardcore URLs to your old address. But, in case if you have your website with your own domain then this would not be a problem.
Its the time to check some other important issues like:
Be sure whether youve a good FTP program with new host servers DNS
Temporary URL of your new host. This is important for checking your website before making change in DNS.
To know about the server environment installed in new host server its very important that you have the right script.
What youll do if run a script? You need to obtain the copy of original installation guide and the script. You need to obtain the listing of server paths like Perl, Send mail, home directory in your new server. For your script if it needs any special type of programs make sure theyre properly installed.
Your site visitors and customers: Dont forget to inform them about your moving plan. Provide them necessary info so they wont feel any problem and same way youll never loss your valuable customers.
The day when you move to the new one: Its recommended to make your move at a time when there is smallest amount of traffic. Its very important to take the backup once again so that youll have your most up-to-date data.
Changing DNS can be done once youll be satisfied. Normally it takes time from 24-48 hours so in between you can make any small changes if you need.
When to cancel your old account? Dont hurry up please! Monitor for about 2 weeks whether the new one is running without problems. Then once youll be sure that all visitors and corresponding emails are coming to your new host server without any interruption then you may cancel your old account.
Source: http://blog.hostome.com/2011/03/05/moving-your-website-hosts-important-factors-you-must-consider/