It's often not as simple as one wants it to be when both artist and client want it to be: Cost efficient, time efficient and quality efficient.
I've often spend my time discussing the best way to handle commissions with clients and artist friends that I came to the conclusion that clarity and understanding is key.
I will divide the guidelines I work with based on 3 commission types.
Book covers ( or illustrations)
Reading all 3 parts will give you the full scope as a lot of it applies to one another as well.
1. Reference board.
If you as a client have very specific characteristic features all set and done for your character it can be very useful for the artist if you'd make them a reference board of art and photos that portray these things.
The artist does not wish for a life story of your cha