This is a useful query that I got from Dmitri Korotkevich's book SQL Server Advanced Troubleshooting:
SELECT TOP 15
[type] AS [Memory Clerk]
,CONVERT(DECIMAL(16,3),SUM(pages_kb) / 1024.0) AS [Memory Usage(MB)]
FROM sys.dm_os_memory_clerks WITH (NOLOCK)
GROUP BY [type]
ORDER BY sum(pages_kb) DESC;
Normally you will see MEMORYCLERK_SQLBUFFERPOOL to be lot bigger than anything else. Exactly how much bigger depends on how much RAM you have available. But let me put it this way: if any other clerk has more than 10 GB of RAM, I find that noticeable.