YOu'll never get rid of it 100% unless you break every face into its own island and relax it and at that point everyone points and laughs at your insane vert count and impossible to create materials.
The best you can do is use as few seams as possible, hide them in logical spots and try to work around the stretching as best as you can by forcing it into areas that don't matter or aren't seen.
If you have long odd triangles sticking off of your UV shells and those tris are in places that don't matter blunt them so that they arrange easier.
there are some 3rd party software solutions that help visualize the distortion like UVLayout but it's a separate program and its not free so I don't see much use for it. Especially when you can apply a custom checker pattern and get a good feel for how the layout stretches.
Remember that maps and materials applied to a highpoly also bake down and account for moderate stretching fairly well. Trying to "draw" that distortion onto the UV layout in photoshop isn't going to go as well.
Also...it helps to put a few extra loops in some of the trouble areas. For instance, using a texture that tiles horizontally on a mesh that bends (like a curved sidewalk or something), the more loops you have in the curve, the easier the bend is and your uvs will come out with less distortion.
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The best you can do is use as few seams as possible, hide them in logical spots and try to work around the stretching as best as you can by forcing it into areas that don't matter or aren't seen.
If you have long odd triangles sticking off of your UV shells and those tris are in places that don't matter blunt them so that they arrange easier.
there are some 3rd party software solutions that help visualize the distortion like UVLayout but it's a separate program and its not free so I don't see much use for it. Especially when you can apply a custom checker pattern and get a good feel for how the layout stretches.
Remember that maps and materials applied to a highpoly also bake down and account for moderate stretching fairly well. Trying to "draw" that distortion onto the UV layout in photoshop isn't going to go as well.