Policies for Custom Work

I’m currently taking a brief hiatus from custom work, but I will begin accepting *limited* commissions again next month. Before I do, I’d like to revamp my policies in order to ensure that all parties have clear/shared expectations for this process. To that end, I would love input from both my customers and my fellow artisans. Here are a few of the topics that I’m pondering:

Customers:
Have you ever commissioned an artist before?
If so, what are your hopes and expectations for this type of transaction?
Are you willing to sign a contract or agreement?
What policies or practices might help you to feel comfortable with the process?
What policies or practices might ensure that you are happy with the end result?

Artisans:

How detailed are your commissions policies?

Do you use a contract, or just a handshake?
Do you require a deposit? If so, how much — and is it refundable?

Do you spell out specifics, such as how many photos and/or revisions are included?
Do you charge for “extras” such as sketches, custom colors, additional photos, multiple revisions, etc?
Do you make a distinction between “customized” (ie – recreating an existing work in custom colors) and “completely custom” (ie – designed from scratch to the customer’s specifications)?

Are there any topics or policies that you feel are critical to a good commission agreement?

Thanks in advance for any input that you can offer!