Christian Cunningham has shared a useful guide to dealing with normal maps.

Christian Cunningham has shared a useful guide to dealing with normal maps. Having a hard time fixing incorrect bakes? Follow these crucial guidelines to bake all your details down into a normal map. 

First of all, there is no perfect way to bake a model, but there are some simple rules that can get you close to perfection. The written tutorial features 7 tricks to help you figure out the process.

Here are the guidelines:

• Only have hard edges on 90 degree edges and higher, everything else must be soft
• Wherever you have hard edges, you must have UV splits as well
• Provide ample padding on your UVs so there is no bleeding
• Before exporting your cage (if you are using floaters) make sure that the normals of the faces are flat
• Even if there is a bevel, where you want a hard edge to appear, smooth it on your low poly. Let your high poly create that crisp edge
• You have to do all of this and continue to worry about correct YV layout and hiding your seams. 
• Export using .obj

Poly Punch

You can get a free copy of the guide with more comments here.