/3/ - 3DCG

>>383693
Keep islands proportional but maintain a certain minimum size.
Arrange the largest islands first.
Keep easy texturing in mind over efficiency. A "good" unwrap doesn't necessarily mean one that's good to texture, pic related. That also means keeping the orientation of the islands upright as often as possible, and clustering similar parts together.

The unwrap in your picture is a bad example. It has a ridiculous amount of duplicate islands that could be stacked.

>>383698
Maya has a good auto layout tool, it's in the UV texture editor. Use that. (but keep in mind that it won't stack identical parts, you have to leave dupes out and then stack them yourself)

>>383704
You have no idea what you're talking about. Every program can layout UVs with a certain distance, and pad the islands while baking. Seamless unwraps are still needed because UV cuts will fuck with your normals and will be visible at lower mips whether you like it or not, no matter how well do you hide them.