Ask HN: Server Management Best Practices

So let's say you have a bunch(or just one) of servers. Is there any good guide or Best Practices on how to be actually a good admin? I'm asking for things like, how you document what software you installed, reporting and monitoring mechanisms/software etc. What do you use for backup and/or do you revision control your configuration files? I'm using an excel sheet at the moment, but I don't think that's the best way. Btw, I'm asking for UNIX systems, but I think most concepts should work also for other systems as well.