Memory\Pages/sec
This counter is a general indicator of how often the system is using the hard drive to store or retrieve memory associated data. If number of pages per second exceeds 50 per paging disk, it indicates downward trend. You can create a trigger which notify you when it's greater than 50.
Memory\Available Bytes
This counter indicates remaining memory after nonpaged pool allocations,
paged pool allocations, process' working sets, and the file system cache have all taken their piece
If the counter is greater than 10% of actual RAM, you are on safe side, you are away from risk zone.
Memory\Page Reads/sec.
This counter is another good indicator of a memory shortage. The counter shows that how often the system is reading from disk. A "sustained" value over 5 page/sec is "often" a strong indicator of a memory shortage. You may see more than 5 page/sec, but you don't have to be worry about that because temporarily, it can be more than 5 page/sec.
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