I do not know how to formally look for memory leaks, but typically it is exemplified by a program that typically takes up a certain amount of memory, usually a low amount, but having that program grow in size over time, to amounts that seem outsized for what that program typically should be. His example of ntoskrnl.exe sitting at 1GB in RAM is a perfect one, as it should never get that large.
Currently, my system has it at 127MB, and that number has risen steadily with system use over the past few hours. Usually the only way to remedy it (other than a software update from the manufacturer), is to restart the affected process, or restart the system.
Windows 10 Home Premium, 64 bit version here. Running great otherwise.