Like Sue says, practice really helps. But you might try holding your yarn in a different way to alter the tension on the yarn. That might enable you to knit more evenly. You might also try needles made out of a different material, because it might change the way the stitches come off the needle as you knit
Also, if you are using natural fibers (plant or animal) blocking can help even up your stitches. Fiber type can have another effect too. Less "springy fibers" such as cotton show unevenness more than more springy ones, like wool.
If you are truly unhappy, keep practicing, and in the mean time you could make some felted bags until your are happier with the way it looks.
And keep in mind that just about everyone has a smidgen of unevenness in their knitting depending on the factors I mentioned above.