For a Non Clustered SQL Server:
Test this all before you do production of course. Take db backups of all dbs before you do this as well and test, test,test your apps.
Stop all unneeded services in Services like Anti Virus, Backup software, IIS, etc....
Make sure all user connections are down as SQLServer will go down and back up during the SP apply.
Simply start the Service pack and walk through the wizard. It does the rest.