The more you knit, the more even your tension. Don't go for any kind of perfection, just knit. You automatically get better.
I'd say my stitches are even and I can follow just about any pattern, but perfect? Never.
As Lana said, we're talking hand knits here. My sweaters from Land's End are more even than my knitting, but then again, if I wanted another Land's End sweater, I'd buy one--probably for less money than I can knit one, too!
The more you knit, the better you get; the better you get, the more you know how to hide/correct mistakes, because there always are some.