Low prices - As a former texturer, I know how hard it is to keep balance between your own profit and affordable cost for the customer. I try to keep my mesh costs low so that derivers can make a decent profit without having a super expensive end product.
Female legs are compatible with thigh boots and garters - Thighs of female meshes match up with standard legs, most thigh high boots and garters will work with them. The D-shape male mesh however has enhanced thighs, so they may not work with all meshes that layer over male thighs.
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 and legs - 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.
You MAY leave your derives derivable! - I do not mind people leaving their derives derivable. So long as I'm still in the derivation chain, I am happy. There may still be some notes on old mesh pages that say not to leave things derivable, but you may disregard that, as of 2011.