Step 1: Prepare the blender jar
You can choose to leave the blender jar as is, meaning a glossy, transparent glass. I think a frosted look adds a little more and helps to diffuse the light so it's not so bright and harsh.
I had this particular jar sandblasted at a local trophy/sign shop. Since I used to work there I got it done for free, so I'm not sure how much something like that would cost. I blasted the inside and out to give it a nice frosted look.