Upgrading SQL Server 2012 from SP2 to SP3 We need to upgrade our SQL Server 2012 from Service Pack 2 to Service Pack 3. We are no database experts and would like to have some info regarding this.
We are going to be doing this upgrade on the lower environments first.
Is there anything we need to specially take care of while or before doing this upgrade. We have checked for the system requirements and we are fine there.
We plan to take a database backup and just run the installation for upgrade and for the latest patches for SP3. Is that all?
Please let me know if we are missing something in here.

Thanks
1/ Microsoft recommends to test it in your UAT environment before proceeding with deployment in production environment.

2/ Backup system &amp; user databases

3/ If you use analysis services backup Analysis Service configuration files, databases and repositories. Backup files present at location
C:\Program Files\Microsoft SQL Server\MSAS11.\OLAP\Data\
C:\Program Files\Microsoft SQL Server\MSAS11.\OLAP\Config\ directory.

4/ Make sure enough space is available on drive where resource/system databases are present. Resource database is utilized during service pack upgrade. 

5/ Service pack upgrade would require a downtime of application. Make sure application does not access database during service pack upgrade. Make sure you stop all jobs and activities on database before proceeding. you don't need to shutdown database services to apply service pack.

6/ Make sure you are administrator on the system and always run the service pack executable with administrator privileges.

Although instructions for SP2 still relvant for SP3 also, please see the below source. I presume this a standalone instance?

Source: http://social.technet.microsoft.com/wiki/contents/articles/25632.how-to-install-sql-server-2012-sp2-on-standalone-sql-server-instance.aspx