Important: Use the Bind Frame to base position of the your character.
Not repeat bone name
Do not repeat the same name for the bones. For handling of the bones in the engine they should be independent names.
Do not create redundant envelopes
Share the vertices of the mesh only with parent or child bones.
Prevent Multi-Sub Objects in your model.
If using animation CPU animation prevent Multi-Subjects in your model, this mode will obtain greatly increase the computing speed of your animation.