How do i keep my eyeliner fom smudging?

I used to have this problem so I know exactly what you're talking about. I changed to liquid liner & i don't have that problem anymore but before I discovered liquid liner, I used take foundation and put it right underneath my lower lash line. Then I'd apply the liner and then add just a little more foundation. The powder actually creates a "barrier" kind of thing so when the liner starts to "fall out", it falls onto the foundation.