Should mesh be 1 part for animated rigging?

Hi thanks for helping me I have a question.
I have a human model that is composed of multiple meshes/objects that are not one piece.
What is the best way to go about getting this group of meshes ready for animated deform rigging? Should it be one mesh for best results? And if so, do I need to join and sew all my objects and meshes together? And if I do what is the quickest way of sewing loops?

it doesn’t have to be one mesh - but it can

it’s easier to weight paint when it is
most of the time, you will have the body as one mesh - and the head a separate mesh
then it will be easier if you do shape keys

the easiest way to sew the loops (if the mesh verts match up)
is to join - ctrl J
then remove doubles in edit mode

hope that helps