Lumber quality problems? Eeek!

So here's my problem.  Every project I take on turns out wonky.  I'm not sure if it's just the lumber I buy (from Home Depot), or if I'm doing something clearly wrong.  It just always seems that no matter how much care I take when cutting, measuring, and fastening together my projects always turn out warped or twisted.  Anything but straight and awesome.  I mean, my mom loves it, because I give everything to her, but I would love to have a project come out perfect and pretty.  How do you guys do it?  I get super envious when I look at all of the brag posts.  

Any help would be appreciated! :D

Oh!  And P.S.:  I really tried to upload some images of my newest project problem, but I couldn't figure out how to.  Woh woh. :(