Max Degree Of Parallelism
This link is probably a good place to start.

Setting the MAXDOP at the server level depends on a lot of things like whether you're using a virtual or physical server, how many physical cores you have, hyperthreading being enabled or not and the number of NUMA nodes you have.  But you if you tinker with that, you should be made aware of increasing your cost threshold for parallelism to a much higher number than the default (5).  This will take a bit of research as to determine at what subtree cost your server typically handles under no parallelism (MAXDOP 1).