Here is a quick checklist for your SQL Server Migration.
1. Build your New Server, Install SQL Server and required updates and keep the server ready for migration
2. Stop Application Service(s) and kill all the connections from sql server.
This is to ensure that the no applications are connected to the Databases during the migration process.
3. Disable all the jobs that refers to this database
4. Take the database to ‘SINGLE_USER’mode
5. Take a FULL backup of all the User databases that are involved in the Migration Process.
6. Move the backups to the destination server or a Shared location, then restore them to the appropriate drives on the destination.
7. Change the compatibility level of the databases (Optional)
Do this if the applications connecting to these databases are independent of the database compatibility level.
8. Transfer logins using SSIS (Transfer Logins Task) or using "sp_help_revlogin"
More information about sp_help_revlogin is at http://support.microsoft.com/kb/246133
9. Check for Orphaned Users in the databases and Fix them (if Any)
10. Update Usage on the migrated Databases
11. Update Stats on the migrated Databases
12. Re-Index or Re-Organize Indexes on the migrated Databases
13. Transfer Jobs using SSIS or manually create them
14. Build Maintenance plans (if Any)
15. Recompile database objects if required
16. Move or rebuild SSIS or DTS packages (if Any)
17. Create Alerts and Operators (if Any)
18. Setup High Availability Options (if Any Like Replication, LogShipping, Mirroring)
19. Test the High Availability options that were setup in the previous step
20. Point the Application(s) to new Server and start the Application Service(s)
21. If the application uses any of the user defined error messages, you may need to copy them to the new server.
22. Test the Application(s)