Besides the actual prescription, it is crucial to know the location of your pupils in the lenses. It is called PD or Pupillary Distance.
Ways to get it:
1) Ask your Doctor! If he or she is a good and honest professional, they will give it to you.
2) Place a small ruler so it would go through the center of your pupils and take a selfie, or ask somebody to take your picture with the ruler. Submit the photo at the checkout along with your prescription.
3) Ask somebody to mark your pupils on the lenses when your frame is on you. Make sure that your eyes and the eyes of the person marking the lenses are at the same level. Look at the tip of the nose of the person marking your lenses. Just ship your frames to us with the markings and your prescription.
I'm busy working on my blog posts. Watch this space!