I have already weight painted and assigned geometry to the left half of my model. I would like to copy thee contents to the right half of the model. How do I this?

I have already weight painted and assigned geometry to the left half of my model. I would like to copy thee contents to the right half of the model. How do I this?

Go to the vertex group panel and choose Copy Vertex Group (from the drop down menu) for each group you want to mirror. Then select the copy and choose Mirror Vertex Group.