SQL Server Min Server Memory using SQL 2008 R2 with SP2 with a server with 64 GB of RAM. I have set max server memory to 58GB considering SQL Server is limited to only database engine related service only. 
I have a question related to setting min server memory 

If I set min server memory to 48 GB does that mean 

a) If windows sends low memory notification to SQL -- SQL server will trims all its pool and try to maintain memory usage up to 48 GB of memory?

b) In case of aggressive working set trimming by windows -- would it leave SQL server's memory usage to 48 GB setting a "floor" for SQL's memory usage. 

c) Are there any recommendation on min server memory? 

Searching the web -- internet has plenty of information for max server memory but only few place I read (Brent Ozar blog for configuration best practices) to set min server memory to 50% of total available RAM on the server.
I would suggest you to leave MIN Server memory to DEFAULT.
Min server memory controls the minimum amount of Physical memory that sql server will try to keep committed. When the SQL Server service starts, it does not acquire all the memory configured in Min Server Memory but instead starts with only the minimum required, growing as necessary. Once memory
usage has increased beyond the Min Server Memory setting, SQL Server won’t release any
memory below that amount.
Bob Dorr explains this settings as :

Min Server Memory


Use the min server memory setting with care.   This is a floor to SQL Server.   Once committed memory to reach the min server memory setting SQL Server won't release memory below the mark.   If you set max server memory to 59GB and min server memory to 56GB, but the server needs to back SQL Server down to 53GB SQL Server won't drop below 56GB.    When you combine this setting with locked pages in memory the memory can't be paged.  This can lead to unwanted performance behaviors and allocation failures.





Searching the web -- internet has plenty of information for max server memory

This is because, this settings is least tuned (people just set it to default), instead max memory is what is generally tuned as it is the &quot;ceiling&quot; for the buffer pool. A good value for max memory will ensure that windows and other processes runing on the server will have enough physical memory to perform their work without forcing sql server to trim.