When they are doing the "which looks better?" part, take your time, don't let them make you feel rushed. When I was younger we didn't have much money, so we had to go to the eye care place inside the local wal-mart. They always made you feel like you were wasting their time, cuz they book too many people. My prescription was never great as a kid.

When I finally got my own money and went to a decent eye place with up to date equipment and no rush, the prescription I got then, and ever since have been literally miles ahead of the wal-mart crap.

My vision was worth the extra 10 dollars and additional 5 minutes. It's a pretty important sense. (Sorry to those who lack the option of sight, but I imagine even you guys have to feel bad for someone that could see perfectly, but has just never gotten the opportunity to).