SQL Server 2008 R2 Resource Managment I have a server running Windows Server 2008 R2 Enterprise 64Bit, with 256 GB RAM. 

I am running SQL Server 2008 R2. With normal usage, SQL Server is using about 232 GB of RAM. 
Occasionally it will creep up approaching 100% RAM usage; this has been causing a lot of problems

I know that I can set maximum server memory usage. I don’t know what to set the usage to. I have been going over the SQL Server documentation and TechNet forums and have not been able to find a best practice or even a consensus as to the correct settings. 

I guess what I am looking for is a SQL Server 2008 R2 resource management best practice guide would someone be able to point me in the right direction, or offer some advice. Thanks in advance.
" Occasionally it will creep up approaching 100% RAM usage; this has
  been causing a lot of problems"


That's often a red herring, as SQL Server will use all of RAM (but will give it back under OS memory pressure). 

Rule of thumb leave 2GB or 5-10% of total physical memory free (Max Memory setting) whichever is larger.

Glenn Berry has a good resource here:


Suggested Max Memory Settings for SQL Server 2005/2008


Also:


A Sys Admins Guide to Microsoft SQL Server Memory 
Wow… An online calculator to misconfigure your SQL Server memory!
How much memory does my SQL Server actually need?
Troubleshooting SQL Server: A Guide for the Accidental DBA
Server Memory Options