Hi, You may refer this article as best practice for SQL Server Adminsitration http://vyaskn.tripod.com/sql_server_administration_best_practices.htm and Idera's Diagnostic Manager is good tool to have in DBA tool kit, also suggest to refer General DBA section and article section (DBA) for more information.
Rather I would ask what is your requirement? What kind of features you need to monitor within your environment, its easy to refer a third party tool. But before that I would incline to see what kind of requirement you have for such monitoring purpose.
We have used DIAB from http://www.diabsqlsoftware.com/ for several years now. We are exceptionally pleased and it has a 69.99 price tag. It covers about everything: Disk, memory, cpu, network, backups, failed jobs, replication. To many to name, check them out. It also monitors multiple servers from a single desktop for no additional cost.
