Enumerate the various stages of Heat treatment for metals?

As you said, there are various stage in the Heat Treatment Process, so it will depend of the what is the view point this question...

You need evaluate some aspects like materials, furnace, mechanical characteristics and proprieties, application of project, cost and others concepts.

However I will go to risk one answer:

1. To define the material

2. To define the type of process (furnace, temperature of austenitization

3. To define the soak time (it will be in reason of geometric characteristic, weight, thickness)

4. To define the type atmosphere neutral, carbonizing or type salt bath

5. To define the type to cooling

Just remembering, heat treatment are process that it can cause enormous prejudice, so then  you must have to search a specialist this science.