This video thoroughly describes the process of setting of a good rig for a character in Blender to be used in Unreal Engine 4. This includes everything from setting up the rig with IK and custom shape control as well as good methods for solving common problems with humanoid rigs.
It furthermore shows a workflow for all humanoid models to use the same skeleton which has great benefits once inside UE4. A description of how to handle animation exporting and such is also described.
I hope you find it useful