The number of enquiries you get each month
Your conversion rate to sale
Your average unit of sale
The number of people who are visiting your website
The number of people that you need to visit your website in order to get an enquiry
The percentage of clients who refer you to others
Etc, etc, etc.
I look at it this way – If you fail to quantify your marketing, how can you test and change things in order to improve your numbers?
And yet most small business do not have a clue what their marketing numbers are!