Low prices - Most of my meshes have a 325 cr submission fee or lower when you go to submit, but none are any higher than 375 cr! I don't have any plans make meshes any more expensive than that, but I may one day if I make something extra special that takes an extensive amount of time to make.
Small file sizes - Some my oldest meshes are not as small in file size, but as I progressed in my learning I made it a point to try to keep file sizes as small as possible for the convenience of developers and end buyers.
Easy to use and well mapped - Another thing I got better at with time, so some older meshes may not be quite as high quality. Wherever possible I stitch maps together so that you do not have to align textures in various areas such as with the default bodyshape how you have to align the textures at the neck and where the thigh connects to the torso. I also try to even out the mapping as much as possible for minimal stretching with movement.
Larger arm map areas for more detail - Wherever possible (and that is the case the majority of the time) the area for the arm textures is increased, allowing for greater texturing detail which is a little closer to the body detail, so your arms don't have to look as fuzzy!
Seamless waists - at a certain point I started making meshes seamless, both the over layers and the skintight layers. Older meshes are not seamless. This is something I started doing more recently though so not quite as many seamless ones from the past.
Compatibility - I only work with the default body shapes for maximum compatibility with other items like jewelry and layerable clothing such as coats, stockings etc. that are great for adding to the versatility of a wardrobe and flexibility in creating one's own look.