Best way to root your Optimus Net from NET10 is to use a program called Unlockroot from unlockroot.com.
I kept looking for a way to root the phone and stumbled across this program and it works wonders. I have had my Optimus Net rooted for about two weeks without one problem whatsoever and it is great. I LOVE HAVING A ROOTED PHONE!!!!!!!
Try this program. It does not work with all phones as of yet, but Optimus Net is one of the phones that it does work for. It will go through the process and then it will ask you to reboot your phone, which does it for you and when it loads back up, SuperUser is installed and your phone is rooted.